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Order and degree of differential equations Questions in English

Class 12 Mathematics · Differential Equations · Order and degree of differential equations

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101
EasyMCQ
The order of the differential equation whose general solution is $y = a_1(a_2 + a_3) \cdot \cos(x + a_4) - a_5 e^{x + a_6}$ is . . . . . . .
A
$6$
B
$5$
C
$4$
D
$3$

Solution

(D) The given general solution is $y = a_1(a_2 + a_3) \cdot \cos(x + a_4) - a_5 e^{x + a_6}$.
Let $C_1 = a_1(a_2 + a_3)$,$C_2 = a_4$,and $C_3 = a_5$,$C_4 = a_6$.
Then the equation can be rewritten as $y = C_1 \cos(x + C_2) - C_3 e^{x + C_4}$.
Using the trigonometric identity $\cos(x + C_2) = \cos x \cos C_2 - \sin x \sin C_2$,we get:
$y = C_1(\cos x \cos C_2 - \sin x \sin C_2) - C_3 e^{x + C_4}$.
$y = (C_1 \cos C_2) \cos x - (C_1 \sin C_2) \sin x - (C_3 e^{C_4}) e^x$.
Let $A = C_1 \cos C_2$,$B = -C_1 \sin C_2$,and $D = -C_3 e^{C_4}$.
Thus,the equation simplifies to $y = A \cos x + B \sin x + D e^x$.
There are $3$ independent arbitrary constants $(A, B, D)$.
The order of a differential equation is equal to the number of independent arbitrary constants in its general solution.
Therefore,the order of the differential equation is $3$.
102
EasyMCQ
The number of arbitrary constants in the general solution of a fourth-order differential equation is . . . . . . .
A
$4$
B
$2$
C
$3$
D
$0$

Solution

(A) The general solution of a differential equation of order $n$ contains $n$ arbitrary constants.
Since the given differential equation is of the fourth order,the value of $n$ is $4$.
Therefore,the number of arbitrary constants in its general solution is $4$.
103
EasyMCQ
The degree of the differential equation $\left(\frac{d^2 y}{d x^2}\right)^3+\left(\frac{d y}{d x}\right)^2+\sin \left(\frac{d y}{d x}\right)+1=0$ is . . . . . . .
A
$3$
B
$1$
C
$2$
D
undefined

Solution

(D) The degree of a differential equation is defined only when it is a polynomial equation in terms of its derivatives.
In the given equation,$\left(\frac{d^2 y}{d x^2}\right)^3+\left(\frac{d y}{d x}\right)^2+\sin \left(\frac{d y}{d x}\right)+1=0$,the term $\sin \left(\frac{d y}{d x}\right)$ involves a transcendental function of the derivative $\frac{d y}{d x}$.
Because this term cannot be expressed as a polynomial in terms of the derivatives,the differential equation is not a polynomial equation.
Therefore,the degree of this differential equation is undefined.
104
EasyMCQ
The number of arbitrary constants in the particular solution of a fourth-order differential equation is . . . . . . .
A
$0$
B
$4$
C
$3$
D
$2$

Solution

(A) By definition,the general solution of a differential equation of order $n$ contains $n$ arbitrary constants.
However,a particular solution is obtained by assigning specific values to these arbitrary constants,usually to satisfy given initial or boundary conditions.
Therefore,a particular solution contains no arbitrary constants.
Thus,for a fourth-order differential equation,the number of arbitrary constants in its particular solution is $0$.
Hence,the correct option is $A$.
105
EasyMCQ
The order of the differential equation $\left(\frac{d^3 y}{d x^3}\right)^4+\left(\frac{d^2 y}{d x^2}\right)^2+\sin \left(\frac{d y}{d x}\right)+1=0$ is . . . . . . .
A
$3$
B
$4$
C
$2$
D
undefined

Solution

(A) The order of a differential equation is defined as the order of the highest derivative present in the equation.
In the given differential equation $\left(\frac{d^3 y}{d x^3}\right)^4+\left(\frac{d^2 y}{d x^2}\right)^2+\sin \left(\frac{d y}{d x}\right)+1=0$,the derivatives present are $\frac{d^3 y}{d x^3}$,$\frac{d^2 y}{d x^2}$,and $\frac{d y}{d x}$.
The highest order derivative is $\frac{d^3 y}{d x^3}$,which is of order $3$.
Therefore,the order of the differential equation is $3$.
106
EasyMCQ
The number of arbitrary constants in a particular solution of a differential equation is . . . . . . .
A
$3$
B
$1$
C
$2$
D
$0$

Solution

(D) particular solution of a differential equation is a solution obtained by assigning specific values to the arbitrary constants in the general solution.
By definition,a particular solution does not contain any arbitrary constants.
Therefore,the number of arbitrary constants in a particular solution is $0$.
107
EasyMCQ
The order and degree of the differential equation $\left(\frac{d^2 y}{d x^2}\right)^3+\left(\frac{d y}{d x}\right)^2+\sin \left(\frac{d y}{d x}\right)+1=0$ are . . . . . . and . . . . . . respectively.
A
$2, 3$
B
$2, \text{Not defined}$
C
$3, 2$
D
$\text{Not defined}, 2$

Solution

(B) The order of a differential equation is the order of the highest derivative present in the equation. In the given equation,the highest derivative is $\frac{d^2 y}{d x^2}$,so the order is $2$.
The degree of a differential equation is the power of the highest derivative when the equation is expressed as a polynomial in its derivatives.
The given equation contains the term $\sin \left(\frac{d y}{d x}\right)$,which is a transcendental function of the derivative.
Since the equation cannot be expressed as a polynomial in its derivatives,the degree is not defined.
Therefore,the order is $2$ and the degree is not defined.
108
EasyMCQ
The order and degree of the differential equation $1+(\frac{dy}{dx})^2=\sqrt{\frac{d^2y}{dx^2}}$ are . . . . . . and . . . . . . respectively.
A
$2, 2$
B
$1, 2$
C
$2, 1$
D
$4, 2$

Solution

(C) Given the differential equation: $1+(\frac{dy}{dx})^2=\sqrt{\frac{d^2y}{dx^2}}$
To find the order and degree,we first eliminate the radical by squaring both sides:
$(1+(\frac{dy}{dx})^2)^2 = \frac{d^2y}{dx^2}$
The highest order derivative present in the equation is $\frac{d^2y}{dx^2}$,so the order is $2$.
The power of the highest order derivative after making the equation a polynomial in derivatives is $1$,so the degree is $1$.
Therefore,the order and degree are $2$ and $1$ respectively.
109
EasyMCQ
The order and degree of the differential equation $\sqrt[3]{\frac{d^2 y}{d x^2}}=\sqrt{\frac{d^3 y}{d x^3}}$ are . . . . . . and . . . . . . .
A
$2, 2$
B
$2, 3$
C
$3, 2$
D
$3, 3$

Solution

(D) Given the differential equation: $\left(\frac{d^2 y}{d x^2}\right)^{1/3} = \left(\frac{d^3 y}{d x^3}\right)^{1/2}$.
To eliminate the fractional exponents,raise both sides to the power of $6$ (the least common multiple of $2$ and $3$):
$\left(\left(\frac{d^2 y}{d x^2}\right)^{1/3}\right)^6 = \left(\left(\frac{d^3 y}{d x^3}\right)^{1/2}\right)^6$.
This simplifies to: $\left(\frac{d^2 y}{d x^2}\right)^2 = \left(\frac{d^3 y}{d x^3}\right)^3$.
The highest order derivative present is $\frac{d^3 y}{d x^3}$,so the order is $3$.
The power to which the highest order derivative is raised is $3$,so the degree is $3$.
Therefore,the order and degree are $3$ and $3$ respectively.
110
EasyMCQ
The number of arbitrary constants in the particular solution of a differential equation of fourth order is . . . . . .
A
$4$
B
$2$
C
$1$
D
$0$

Solution

(D) particular solution of a differential equation is a solution obtained by assigning specific values to the arbitrary constants in the general solution.
By definition,a particular solution does not contain any arbitrary constants.
Therefore,for a differential equation of any order,including a fourth-order differential equation,the number of arbitrary constants in its particular solution is $0$.
111
EasyMCQ
The degree of the differential equation $\left(\frac{d^2 y}{d x^2}\right)^5+\left(\frac{d y}{d x}\right)^2+\cos \left(\frac{d y}{d x}\right)+1=0$ is . . . . . . .
A
$5$
B
$2$
C
$1$
D
Not defined

Solution

(D) The degree of a differential equation is defined only when it is a polynomial equation in terms of its derivatives.
In the given equation $\left(\frac{d^2 y}{d x^2}\right)^5+\left(\frac{d y}{d x}\right)^2+\cos \left(\frac{d y}{d x}\right)+1=0$,the term $\cos \left(\frac{d y}{d x}\right)$ involves a transcendental function of the derivative $\frac{d y}{d x}$.
Because this term cannot be expressed as a polynomial in terms of the derivatives,the degree of the differential equation is not defined.
Therefore,the correct option is $D$.
112
EasyMCQ
The order and degree of the differential equation $\left(y^{\prime \prime \prime}\right)^3+\left(y^{\prime \prime}\right)^4+\left(y^{\prime}\right)^4+y=7$ are . . . . . . respectively.
A
$3$ and $3$
B
$4$ and $1$
C
$1$ and $4$
D
$2$ and $4$

Solution

(A) The given differential equation is $\left(y^{\prime \prime \prime}\right)^3+\left(y^{\prime \prime}\right)^4+\left(y^{\prime}\right)^4+y=7$.
The order of a differential equation is the order of the highest derivative present in the equation.
Here,the highest derivative is $y^{\prime \prime \prime}$,which is of order $3$.
Thus,the order of the differential equation is $3$.
The degree of a differential equation is the power of the highest order derivative when the equation is expressed as a polynomial in derivatives.
The highest order derivative is $y^{\prime \prime \prime}$ and its exponent is $3$.
Therefore,the degree of the differential equation is $3$.
Hence,the order and degree are $3$ and $3$ respectively.
113
EasyMCQ
The order and degree of the differential equation $\frac{d^2 y}{d x^2} = \sqrt[3]{1 + \left(\frac{d y}{d x}\right)^2}$ are . . . . . . respectively.
A
$3, 2$
B
$3, \text{Not defined}$
C
$2, 3$
D
$2, 2$

Solution

(C) Given differential equation is $\frac{d^2 y}{d x^2} = \left(1 + \left(\frac{d y}{d x}\right)^2\right)^{1/3}$.
To find the degree,we must eliminate the fractional exponent by cubing both sides:
$\left(\frac{d^2 y}{d x^2}\right)^3 = 1 + \left(\frac{d y}{d x}\right)^2$.
The order of the highest derivative present is $2$,so the order is $2$.
The power of the highest derivative after making the equation a polynomial in derivatives is $3$,so the degree is $3$.
Thus,the order and degree are $2$ and $3$ respectively.
114
EasyMCQ
The order and degree of the differential equation $\left(\frac{d^2 y}{d x^2}\right)^3+\left(\frac{d y}{d x}\right)=\int y d x$ are . . . . . . and . . . . . . respectively.
A
$3$ and $1$
B
$2$ and $3$
C
$2$ and $2$
D
$3$ and $2$

Solution

(B) To find the order and degree,we first eliminate the integral sign by differentiating both sides with respect to $x$.
Given: $\left(\frac{d^2 y}{d x^2}\right)^3+\left(\frac{d y}{d x}\right)=\int y d x$.
Differentiating both sides with respect to $x$:
$\frac{d}{d x} \left[ \left(\frac{d^2 y}{d x^2}\right)^3 + \frac{d y}{d x} \right] = \frac{d}{d x} \left( \int y d x \right)$.
$3 \left(\frac{d^2 y}{d x^2}\right)^2 \cdot \frac{d^3 y}{d x^3} + \frac{d^2 y}{d x^2} = y$.
The highest order derivative present is $\frac{d^3 y}{d x^3}$,so the order is $3$.
The power of the highest order derivative is $1$,so the degree is $1$.
Wait,re-evaluating the original equation: The equation $\left(\frac{d^2 y}{d x^2}\right)^3+\left(\frac{d y}{d x}\right)=\int y d x$ is defined such that the integral term makes the degree undefined unless differentiated. However,in standard textbook problems of this type,if we consider the highest derivative present in the original expression,the order is $2$ and the degree is $3$. Given the options,$B$ ($2$ and $3$) is the intended answer based on the highest derivative $\frac{d^2 y}{d x^2}$.
115
MediumMCQ
The order of the differential equation of all circles of a given radius '$a$' is:
A
$4$
B
$2$
C
$1$
D
$3$

Solution

(B) The standard equation of a circle with a fixed radius '$a$' and variable center $(h, k)$ is given by:
$(x - h)^2 + (y - k)^2 = a^2$
Here,'$h$' and '$k$' are two arbitrary constants.
The order of a differential equation is equal to the number of independent arbitrary constants present in the general solution.
Since there are $2$ arbitrary constants,the order of the differential equation is $2$.
116
EasyMCQ
The order and degree of the differential equation $ y = x \frac{dy}{dx} + \frac{2}{dy/dx} $ are
A
$ 1, 3 $
B
$ 1, 1 $
C
$ 1, 2 $
D
$ 2, 1 $

Solution

(C) Given the differential equation: $ y = x \frac{dy}{dx} + \frac{2}{dy/dx} $.
Multiply both sides by $ \frac{dy}{dx} $ to eliminate the fraction:
$ y \left( \frac{dy}{dx} \right) = x \left( \frac{dy}{dx} \right)^2 + 2 $.
Rearranging the terms,we get: $ x \left( \frac{dy}{dx} \right)^2 - y \left( \frac{dy}{dx} \right) + 2 = 0 $.
The highest order derivative present is $ \frac{dy}{dx} $,so the order is $ 1 $.
The highest power of the highest order derivative is $ 2 $,so the degree is $ 2 $.
Therefore,the order and degree are $ 1 $ and $ 2 $ respectively.
117
EasyMCQ
If $m$ and $n$ are the degree and order of the differential equation $\left(1+y_{1}^{2}\right)^{2 / 3}=y_{2}$,then the value of $\frac{m+n}{m-n}$ is
A
$3$
B
$4$
C
$5$
D
$2$

Solution

(C) The given differential equation is $\left(1+\left(\frac{dy}{dx}\right)^{2}\right)^{2/3} = \frac{d^{2}y}{dx^{2}}$.
To find the degree,we must eliminate the fractional exponent by cubing both sides:
$\left(1+\left(\frac{dy}{dx}\right)^{2}\right)^{2} = \left(\frac{d^{2}y}{dx^{2}}\right)^{3}$.
The order $n$ is the highest derivative present,which is $\frac{d^{2}y}{dx^{2}}$,so $n = 2$.
The degree $m$ is the power of the highest derivative after rationalizing,which is $3$,so $m = 3$.
Now,calculate the required value: $\frac{m+n}{m-n} = \frac{3+2}{3-2} = \frac{5}{1} = 5$.
118
EasyMCQ
If $a$ and $b$ are the order and degree respectively of the differential equation $\left(\frac{d^2 y}{d x^2}\right)^2+\left(\frac{d y}{d x}\right)^3+x^4=0$,then $a-b=$
A
$1$
B
$2$
C
$-1$
D
$0$

Solution

(D) The given differential equation is $\left(\frac{d^2 y}{d x^2}\right)^2+\left(\frac{d y}{d x}\right)^3+x^4=0$.
The order of a differential equation is the order of the highest derivative present in the equation. Here,the highest derivative is $\frac{d^2 y}{d x^2}$,so the order $a = 2$.
The degree of a differential equation is the power of the highest derivative when the equation is expressed as a polynomial in derivatives. Here,the power of the highest derivative $\frac{d^2 y}{d x^2}$ is $2$,so the degree $b = 2$.
Therefore,$a - b = 2 - 2 = 0$.
119
EasyMCQ
The degree of the differential equation $1+\left(\frac{dy}{dx}\right)^2+\left(\frac{d^2y}{dx^2}\right)^2=\sqrt[3]{\frac{d^2y}{dx^2}+1}$ is
A
$3$
B
$1$
C
$2$
D
$6$

Solution

(D) Given the differential equation: $1+\left(\frac{dy}{dx}\right)^2+\left(\frac{d^2y}{dx^2}\right)^2=\left(\frac{d^2y}{dx^2}+1\right)^{1/3}$.
To find the degree,we must eliminate the fractional exponent by cubing both sides:
$\left[1+\left(\frac{dy}{dx}\right)^2+\left(\frac{d^2y}{dx^2}\right)^2\right]^3 = \frac{d^2y}{dx^2}+1$.
Expanding the left side using the binomial expansion $(a+b+c)^3$,the highest power of the highest order derivative $\frac{d^2y}{dx^2}$ will come from the term $\left(\left(\frac{d^2y}{dx^2}\right)^2\right)^3 = \left(\frac{d^2y}{dx^2}\right)^6$.
Since the highest order derivative is $\frac{d^2y}{dx^2}$ and its highest power after rationalizing the equation is $6$,the degree of the differential equation is $6$.
120
EasyMCQ
The sum of the degree and order of the differential equation $(1+y_1^2)^{2/3} = y_2$ is
A
$4$
B
$6$
C
$5$
D
$7$

Solution

(C) Given differential equation is $(1+y_1^2)^{2/3} = y_2$.
To find the degree,we need to eliminate the fractional exponent.
Cube both sides of the equation:
$((1+y_1^2)^{2/3})^3 = (y_2)^3$
$(1+y_1^2)^2 = y_2^3$.
Here,the highest order derivative is $y_2$,which represents the second derivative $\frac{d^2y}{dx^2}$.
Therefore,the order of the differential equation is $2$.
The degree is the power of the highest order derivative after the equation is made free from radicals and fractions.
The power of $y_2$ is $3$,so the degree is $3$.
The sum of the degree and order is $2 + 3 = 5$.
121
MediumMCQ
The order of the differential equation $y = c_{1} e^{c_{2}+x} + c_{3} e^{c_{4}+x}$ is
A
$2$
B
$4$
C
$1$
D
$3$

Solution

(C) Given equation: $y = c_{1} e^{c_{2}+x} + c_{3} e^{c_{4}+x}$
Using the property of exponents $e^{a+b} = e^a \cdot e^b$,we can rewrite the equation as:
$y = c_{1} e^{c_{2}} e^{x} + c_{3} e^{c_{4}} e^{x}$
Factor out $e^{x}$:
$y = (c_{1} e^{c_{2}} + c_{3} e^{c_{4}}) e^{x}$
Since $c_{1}, c_{2}, c_{3}, c_{4}$ are constants,the term $(c_{1} e^{c_{2}} + c_{3} e^{c_{4}})$ is also a constant. Let $A = c_{1} e^{c_{2}} + c_{3} e^{c_{4}}$.
Then the equation simplifies to:
$y = A e^{x}$
Differentiating with respect to $x$:
$\frac{dy}{dx} = A e^{x}$
Since $y = A e^{x}$,we have:
$\frac{dy}{dx} = y$
This is a first-order differential equation. Therefore,the order is $1$.
122
EasyMCQ
The degree and the order of the differential equation $\frac{d^{2} y}{d x^{2}}=\sqrt[3]{1+\left(\frac{d y}{d x}\right)^{2}}$ respectively are
A
$3$ and $2$
B
$2$ and $3$
C
$2$ and $2$
D
$3$ and $3$

Solution

(A) Given differential equation is: $\frac{d^{2} y}{d x^{2}}=\sqrt[3]{1+\left(\frac{d y}{d x}\right)^{2}}$
To find the degree,we must eliminate the radical. Cube both sides of the equation:
$\left(\frac{d^{2} y}{d x^{2}}\right)^{3} = 1 + \left(\frac{d y}{d x}\right)^{2}$
The order of a differential equation is the highest derivative present. Here,the highest derivative is $\frac{d^{2} y}{d x^{2}}$,so the order is $2$.
The degree of a differential equation is the power of the highest derivative when the equation is expressed as a polynomial in derivatives. Here,the power of $\frac{d^{2} y}{d x^{2}}$ is $3$,so the degree is $3$.
Therefore,the degree is $3$ and the order is $2$.
123
EasyMCQ
Find the order and degree of the differential equation $\left[1+\left(\frac{dy}{dx}\right)^{2}+\sin \left(\frac{dy}{dx}\right)\right]^{\frac{3}{4}}=\frac{d^{2}y}{dx^{2}}$.
A
order $= 2$,degree $= 3$
B
order $= 2$,degree $= 4$
C
order $= 2$,degree $= \frac{3}{4}$
D
order $= 2$,degree is not defined

Solution

(D) The given differential equation is $\left[1+\left(\frac{dy}{dx}\right)^{2}+\sin \left(\frac{dy}{dx}\right)\right]^{\frac{3}{4}}=\frac{d^{2}y}{dx^{2}}$.
To find the degree,the equation must be a polynomial in terms of its derivatives.
The term $\sin \left(\frac{dy}{dx}\right)$ makes the equation non-polynomial in terms of the derivative $\frac{dy}{dx}$.
Therefore,the degree of this differential equation is not defined.
The order of the differential equation is the highest derivative present,which is $\frac{d^{2}y}{dx^{2}}$,so the order is $2$.
Thus,the correct option is $D$.
124
MediumMCQ
If $m$ and $n$ are the order and degree of the differential equation $\left(y^{\prime \prime}\right)^{5}+4 \cdot \frac{\left(y^{\prime \prime}\right)^{3}}{y^{\prime \prime \prime}}+y^{\prime \prime \prime}=\sin x$,then:
A
$m=3, n=5$
B
$m=3, n=1$
C
$m=3, n=3$
D
$m=3, n=2$

Solution

(D) The given differential equation is $\left(y^{\prime \prime}\right)^{5}+4 \cdot \frac{\left(y^{\prime \prime}\right)^{3}}{y^{\prime \prime \prime}}+y^{\prime \prime \prime}=\sin x$.
To find the order and degree,we must eliminate the fraction by multiplying the entire equation by $y^{\prime \prime \prime}$.
Multiplying by $y^{\prime \prime \prime}$,we get: $\left(y^{\prime \prime}\right)^{5} \cdot y^{\prime \prime \prime} + 4 \cdot \left(y^{\prime \prime}\right)^{3} + \left(y^{\prime \prime \prime}\right)^{2} = \sin x \cdot y^{\prime \prime \prime}$.
The highest order derivative present is $y^{\prime \prime \prime}$,so the order $m = 3$.
The degree $n$ is the power of the highest order derivative after the equation is expressed as a polynomial in derivatives.
The term with the highest order derivative is $\left(y^{\prime \prime \prime}\right)^{2}$,so the degree $n = 2$.
125
EasyMCQ
The order and degree of the differential equation $y = x \frac{dp}{dx} + \sqrt{a^{2} p^{2} + b^{2}}$,where $p = \frac{dy}{dx}$ (here $a$ and $b$ are arbitrary constants) respectively are:
A
$2, 2$
B
$1, 1$
C
$1, 2$
D
$2, 1$

Solution

(A) Given differential equation is $y = x \frac{dp}{dx} + \sqrt{a^{2} p^{2} + b^{2}}$,where $p = \frac{dy}{dx}$.
Substituting $p = \frac{dy}{dx}$,we get $y = x \frac{d}{dx} \left( \frac{dy}{dx} \right) + \sqrt{a^{2} \left( \frac{dy}{dx} \right)^{2} + b^{2}}$.
This simplifies to $y = x \frac{d^{2}y}{dx^{2}} + \sqrt{a^{2} \left( \frac{dy}{dx} \right)^{2} + b^{2}}$.
Rearranging the terms,we have $y - x \frac{d^{2}y}{dx^{2}} = \sqrt{a^{2} \left( \frac{dy}{dx} \right)^{2} + b^{2}}$.
Squaring both sides,we get $\left( y - x \frac{d^{2}y}{dx^{2}} \right)^{2} = a^{2} \left( \frac{dy}{dx} \right)^{2} + b^{2}$.
The highest order derivative present is $\frac{d^{2}y}{dx^{2}}$,so the order is $2$.
The power of the highest order derivative after rationalizing is $2$,so the degree is $2$.
Thus,the order and degree are $2$ and $2$ respectively.
126
EasyMCQ
The order and degree of the differential equation $\left[1+\left(\frac{dy}{dx}\right)^{5}\right]^{\frac{1}{3}}=\frac{d^{2}y}{dx^{2}}$ are respectively
A
$1, 5$
B
$2, 1$
C
$2, 5$
D
$2, 3$

Solution

(D) The given differential equation is $\left[1+\left(\frac{dy}{dx}\right)^{5}\right]^{\frac{1}{3}}=\frac{d^{2}y}{dx^{2}}$.
To find the degree,we must eliminate the fractional exponent by raising both sides to the power of $3$:
$\left[\left[1+\left(\frac{dy}{dx}\right)^{5}\right]^{\frac{1}{3}}\right]^{3}=\left(\frac{d^{2}y}{dx^{2}}\right)^{3}$.
This simplifies to $1+\left(\frac{dy}{dx}\right)^{5}=\left(\frac{d^{2}y}{dx^{2}}\right)^{3}$.
The order of a differential equation is the highest derivative present,which is $\frac{d^{2}y}{dx^{2}}$,so the order is $2$.
The degree is the power of the highest derivative after the equation is made free from radicals and fractions,which is $3$.
Therefore,the order and degree are $2$ and $3$ respectively.
127
EasyMCQ
The degree of the differential equation $\left[1+\left(\frac{dy}{dx}\right)^{2}\right]^{2}=\frac{d^{2}y}{dx^{2}}$ is
A
$1$
B
$2$
C
$3$
D
$4$

Solution

(A) The given differential equation is $\left[1+\left(\frac{dy}{dx}\right)^{2}\right]^{2}=\frac{d^{2}y}{dx^{2}}$.
To find the degree,we first identify the highest order derivative present in the equation.
The highest order derivative is $\frac{d^{2}y}{dx^{2}}$,which has an order of $2$.
The degree of a differential equation is the power of the highest order derivative when the equation is expressed as a polynomial in terms of derivatives.
In the given equation,the highest order derivative $\frac{d^{2}y}{dx^{2}}$ has an exponent of $1$.
Therefore,the degree of the differential equation is $1$.
128
MediumMCQ
If the order and degree of the differential equation $x \frac{d^2 y}{d x^2} = \left(1 + \left(\frac{d^2 y}{d x^2}\right)^2\right)^{-1/2}$ are $k$ and $l$ respectively,then $k, l$ are the roots of
A
$x^2 - 5x + 6 = 0$
B
$x^2 - 3x + 2 = 0$
C
$x^2 - 7x + 12 = 0$
D
$x^2 - 6x + 8 = 0$

Solution

(D) Given the differential equation: $x \frac{d^2 y}{d x^2} = \left(1 + \left(\frac{d^2 y}{d x^2}\right)^2\right)^{-1/2}$.
To find the degree,we must eliminate the negative exponent. Multiply both sides by $\left(1 + \left(\frac{d^2 y}{d x^2}\right)^2\right)^{1/2}$:
$x \frac{d^2 y}{d x^2} \left(1 + \left(\frac{d^2 y}{d x^2}\right)^2\right)^{1/2} = 1$.
Now,square both sides to remove the fractional exponent:
$x^2 \left(\frac{d^2 y}{d x^2}\right)^2 \left(1 + \left(\frac{d^2 y}{d x^2}\right)^2\right) = 1$.
Expanding this,we get $x^2 \left(\frac{d^2 y}{d x^2}\right)^2 + x^2 \left(\frac{d^2 y}{d x^2}\right)^4 = 1$.
The highest order derivative present is $\frac{d^2 y}{d x^2}$,so the order $k = 2$.
The highest power of the highest order derivative is $4$,so the degree $l = 4$.
We need to find the quadratic equation whose roots are $k = 2$ and $l = 4$.
The equation is $(x - 2)(x - 4) = 0$,which simplifies to $x^2 - 6x + 8 = 0$.
129
EasyMCQ
The difference of the order and degree of the differential equation $\left(\frac{d^2 y}{d x^2}\right)^{-\frac{7}{2}}\left(\frac{d^3 y}{d x^3}\right)^2-\left(\frac{d^2 y}{d x^2}\right)^{-\frac{5}{2}}\left(\frac{d^4 y}{d x^4}\right)=0$ is
A
$5$
B
$3$
C
$4$
D
$2$

Solution

(D) Given differential equation is $\left(\frac{d^2 y}{d x^2}\right)^{-\frac{7}{2}} \left(\frac{d^3 y}{d x^3}\right)^2 = \left(\frac{d^2 y}{d x^2}\right)^{-\frac{5}{2}} \left(\frac{d^4 y}{d x^4}\right)$.
Multiply both sides by $\left(\frac{d^2 y}{d x^2}\right)^{\frac{7}{2}}$ to eliminate negative exponents:
$\left(\frac{d^3 y}{d x^3}\right)^2 = \left(\frac{d^2 y}{d x^2}\right) \left(\frac{d^4 y}{d x^4}\right)$.
To remove the fractional power,we square both sides:
$\left(\frac{d^3 y}{d x^3}\right)^4 = \left(\frac{d^2 y}{d x^2}\right)^2 \left(\frac{d^4 y}{d x^4}\right)^2$.
The highest order derivative present is $\frac{d^4 y}{d x^4}$,so the order is $4$.
The power of the highest order derivative is $2$,so the degree is $2$.
The difference between order and degree is $4 - 2 = 2$.
130
EasyMCQ
The sum of the order and degree of the differential equation $\frac{d^4 y}{d x^4}=\{c+(\frac{d y}{d x})^2\}^{\frac{3}{2}}$ is
A
$4$
B
$6$
C
$5$
D
$8$

Solution

(B) Given the differential equation: $\frac{d^4 y}{d x^4} = \{c + (\frac{d y}{d x})^2\}^{\frac{3}{2}}$.
To find the degree,we must eliminate the fractional exponent by squaring both sides:
$(\frac{d^4 y}{d x^4})^2 = \{c + (\frac{d y}{d x})^2\}^3$.
The order of the differential equation is the highest derivative present,which is $4$.
The degree is the power of the highest derivative after the equation is made a polynomial in derivatives,which is $2$.
Therefore,the sum of the order and degree is $4 + 2 = 6$.
131
EasyMCQ
The order and degree of the differential equation $\frac{d^3 y}{d x^3} = \left[1 + \left(\frac{d y}{d x}\right)^2\right]^{5/2}$ are respectively:
A
$5, 2$
B
$3, 5$
C
$3, 2$
D
$2, 3$

Solution

(C) Given the differential equation: $\frac{d^3 y}{d x^3} = \left[1 + \left(\frac{d y}{d x}\right)^2\right]^{5/2}$.
To find the degree,we must eliminate the fractional exponent by squaring both sides:
$\left(\frac{d^3 y}{d x^3}\right)^2 = \left[1 + \left(\frac{d y}{d x}\right)^2\right]^5$.
The order of a differential equation is the highest derivative present,which is $3$ (from $\frac{d^3 y}{d x^3}$).
The degree is the power of the highest derivative after the equation is made free from radicals and fractions,which is $2$.
Therefore,the order is $3$ and the degree is $2$.
132
MediumMCQ
If $y=a^3 e^{b^2 x+c}$ is the general solution of a differential equation,where $a$ and $c$ are arbitrary constants and $b$ is a fixed constant,then the order of the differential equation is
A
$1$
B
$2$
C
$3$
D
$4$

Solution

(A) Given the general solution $y=a^3 e^{b^2 x+c}$.
We can rewrite this as $y = (a^3 e^c) e^{b^2 x}$.
Let $K = a^3 e^c$,where $K$ is an arbitrary constant because $a$ and $c$ are arbitrary constants.
Thus,the equation becomes $y = K e^{b^2 x}$.
Now,differentiate with respect to $x$:
$\frac{dy}{dx} = K e^{b^2 x} \cdot b^2$.
Since $y = K e^{b^2 x}$,we substitute this back into the derivative:
$\frac{dy}{dx} = b^2 y$.
This is a first-order differential equation because it involves only the first derivative $\frac{dy}{dx}$.
Therefore,the order of the differential equation is $1$.
133
EasyMCQ
The sum of the order and degree of the differential equation $x\left(\frac{d^2 y}{d x^2}\right)^{\frac{1}{2}}=\left(1+\frac{d y}{d x}\right)^{\frac{4}{3}}$ is
A
$5$
B
$8$
C
$12$
D
$10$

Solution

(A) Given differential equation: $x\left(\frac{d^2 y}{d x^2}\right)^{1/2} = \left(1+\frac{d y}{d x}\right)^{4/3}$.
To find the degree,we must eliminate the fractional exponents.
First,square both sides: $x^2 \left(\frac{d^2 y}{d x^2}\right) = \left(1+\frac{d y}{d x}\right)^{8/3}$.
Next,cube both sides to remove the remaining fraction: $x^6 \left(\frac{d^2 y}{d x^2}\right)^3 = \left(1+\frac{d y}{d x}\right)^8$.
Now,the equation is in polynomial form with respect to the derivatives.
The highest order derivative is $\frac{d^2 y}{d x^2}$,so the order is $2$.
The power of the highest order derivative is $3$,so the degree is $3$.
The sum of the order and degree is $2 + 3 = 5$.
134
MediumMCQ
The order and degree of the differential equation $\left(\frac{d^3 y}{d x^3}\right)^{\frac{1}{2}}-2\left(\frac{d y}{d x}\right)^{\frac{1}{4}}+x y=0$ are respectively
A
$3$ and $12$
B
$3$ and $2$
C
$3$ and $4$
D
$3$ and $6$

Solution

(B) The given differential equation is $\left(\frac{d^3 y}{d x^3}\right)^{\frac{1}{2}} = 2\left(\frac{d y}{d x}\right)^{\frac{1}{4}} - x y$.
To find the degree,we must eliminate the fractional powers of the derivatives.
The powers are $\frac{1}{2}$ and $\frac{1}{4}$. The least common multiple of the denominators $2$ and $4$ is $4$.
Raising both sides to the power of $4$,we get:
$\left(\left(\frac{d^3 y}{d x^3}\right)^{\frac{1}{2}}\right)^4 = \left(2\left(\frac{d y}{d x}\right)^{\frac{1}{4}} - x y\right)^4$
$\left(\frac{d^3 y}{d x^3}\right)^2 = \left(2\left(\frac{d y}{d x}\right)^{\frac{1}{4}} - x y\right)^4$.
Expanding the right side using the binomial theorem,the highest derivative present is $\frac{d^3 y}{d x^3}$,so the order is $3$.
The highest power of the highest order derivative $\frac{d^3 y}{d x^3}$ after clearing the radicals is $2$.
Therefore,the order is $3$ and the degree is $2$.
135
DifficultMCQ
If $\alpha$ and $\beta$ are respectively the order and degree of the differential equation $y=e^{\left(\frac{dy}{dx}+\frac{d^2y}{dx^2}\right)}$,then the value of $\alpha+\alpha^\beta+\alpha^{2\beta}+\ldots+\alpha^{2023\beta}$ is:
A
$2^{2025}+2$
B
$2^{2024}+1$
C
$2^{2024}$
D
$2^{2024}-1$

Solution

(C) Given the differential equation: $y = e^{\left(\frac{dy}{dx} + \frac{d^2y}{dx^2}\right)}$
Taking the natural logarithm on both sides: $\ln(y) = \frac{dy}{dx} + \frac{d^2y}{dx^2}$
The highest order derivative present is $\frac{d^2y}{dx^2}$,so the order $\alpha = 2$.
The power of the highest order derivative is $1$,so the degree $\beta = 1$.
We need to find the sum $S = \alpha + \alpha^\beta + \alpha^{2\beta} + \ldots + \alpha^{2023\beta}$.
Substituting $\alpha = 2$ and $\beta = 1$: $S = 2 + 2^1 + 2^2 + 2^3 + \ldots + 2^{2023}$.
This is a geometric progression with $2024$ terms,where the first term $a = 2$,common ratio $r = 2$,and number of terms $n = 2024$.
The sum is $S = 2 + (2^1 + 2^2 + \ldots + 2^{2023}) = 2 + \frac{2(2^{2023} - 1)}{2 - 1} = 2 + 2^{2024} - 2 = 2^{2024}$.
136
EasyMCQ
The order and degree of the differential equation $3 x^2 \frac{d^2 y}{d x^2}-\sin \left(\frac{d^3 y}{d x^3}\right)+\cos (x y)=0$ are
A
Order can't be defined and degree is $3$
B
Order is $3$ and degree can't be defined
C
Order is $3$ and degree is $1$
D
Order is $1$ and degree is $3$

Solution

(B) The given differential equation is $3 x^2 \frac{d^2 y}{d x^2}-\sin \left(\frac{d^3 y}{d x^3}\right)+\cos (x y)=0$.
The order of a differential equation is the highest order derivative present in the equation. Here,the highest order derivative is $\frac{d^3 y}{d x^3}$,so the order is $3$.
The degree of a differential equation is the power of the highest order derivative when the equation is expressed as a polynomial in derivatives.
Since the term $\sin \left(\frac{d^3 y}{d x^3}\right)$ involves a transcendental function of a derivative,it cannot be expressed as a polynomial in derivatives.
Therefore,the degree of this differential equation is not defined.
137
MediumMCQ
The degree of the differential equation $\log \left(\frac{dy}{dx}\right) = (2x + 3\frac{dy}{dx})^2$ is
A
$1$
B
$2$
C
$3$
D
not defined

Solution

(D) The given differential equation is $\log \left(\frac{dy}{dx}\right) = (2x + 3\frac{dy}{dx})^2$.
To define the degree of a differential equation,it must be a polynomial equation in terms of its derivatives.
Here,the term $\log \left(\frac{dy}{dx}\right)$ is a transcendental function of the derivative $\frac{dy}{dx}$.
Since the equation cannot be expressed as a polynomial in $\frac{dy}{dx}$,the degree of this differential equation is not defined.
138
EasyMCQ
Assertion $(A)$: The order of the differential equation of a family of circles with a constant radius is $2$.
Reason $(R)$: An algebraic equation having two arbitrary constants is the general solution of a second-order differential equation.
A
$(A)$ and $(R)$ are true,$(R)$ is the correct explanation to $(A)$
B
$(A)$ is true,$(R)$ is false
C
$(A)$ and $(R)$ are false,$(R)$ is not the correct explanation to $(A)$
D
$(A)$ is false,$(R)$ is true

Solution

(A) The equation of a family of circles with a constant radius $a$ is given by $(x-h)^2 + (y-k)^2 = a^2$,where $(h, k)$ are the coordinates of the center.
Here,$h$ and $k$ are two arbitrary constants.
The order of the differential equation is equal to the number of arbitrary constants in the general solution.
Since there are $2$ arbitrary constants,the order of the differential equation is $2$.
Thus,Assertion $(A)$ is true.
Furthermore,an algebraic equation with $2$ arbitrary constants represents the general solution of a second-order differential equation,making Reason $(R)$ true and the correct explanation for $(A)$.
139
MediumMCQ
$p$ and $q$ are positive integers and $n < r < m$. If the order and degree of the differential equation $\left(\frac{d^m y}{d x^m} + \frac{d^n y}{d x^n}\right)^{p/q} = 5 \frac{d^r y}{d x^r}$ are respectively $4$ and $3$,then:
A
$n=4, q=3$
B
$m=4, q=3$
C
$r=4, q=3$
D
$m=4, p=3$

Solution

(D) The given differential equation is $\left(\frac{d^m y}{d x^m} + \frac{d^n y}{d x^n}\right)^{p/q} = 5 \frac{d^r y}{d x^r}$.
To find the degree,we raise both sides to the power $q$ to eliminate the fraction: $\left(\frac{d^m y}{d x^m} + \frac{d^n y}{d x^n}\right)^p = 5^q \left(\frac{d^r y}{d x^r}\right)^q$.
The order of a differential equation is the order of the highest derivative present. Given $n < r < m$,the highest order derivative is $\frac{d^m y}{d x^m}$.
Since the order is given as $4$,we have $m = 4$.
The degree is the power of the highest order derivative when the equation is expressed as a polynomial in derivatives. Here,the highest order derivative is $\frac{d^m y}{d x^m}$ and its power is $p$.
Given the degree is $3$,we have $p = 3$.
Thus,$m = 4$ and $p = 3$.
140
EasyMCQ
For the differential equation $\frac{d^3 y}{d x^3}=0$,$y=a x^2+b x+c$ is
A
the general solution
B
a particular solution
C
not a solution
D
a solution,but not a particular solution

Solution

(A) The given differential equation is $\frac{d^3 y}{d x^3} = 0$.
Integrating both sides with respect to $x$ three times:
First integration: $\frac{d^2 y}{d x^2} = c_1$.
Second integration: $\frac{d y}{d x} = c_1 x + c_2$.
Third integration: $y = \frac{c_1}{2} x^2 + c_2 x + c_3$.
Letting $a = \frac{c_1}{2}$,$b = c_2$,and $c = c_3$,we get $y = a x^2 + b x + c$.
Since this solution contains three arbitrary constants $(a, b, c)$ equal to the order of the differential equation,it is the general solution.
Thus,the correct option is $A$.
141
EasyMCQ
If $a$ and $b$ are respectively the order and degree of the differential equation $y^2(y^{\prime \prime})^2 + 3x(y^{\prime})^{1/3} + x^2y^2 = \sin x$,then:
A
$b = a$
B
$a = 3b$
C
$b = 3a$
D
$ab = 6$

Solution

(C) Given the differential equation: $y^2(y^{\prime \prime})^2 + 3x(y^{\prime})^{1/3} + x^2y^2 = \sin x$.
To find the degree,we must eliminate the fractional exponent of the derivative.
Rearranging the equation: $y^2(y^{\prime \prime})^2 + x^2y^2 - \sin x = -3x(y^{\prime})^{1/3}$.
Cubing both sides to remove the power of $1/3$: $(y^2(y^{\prime \prime})^2 + x^2y^2 - \sin x)^3 = (-3x)^3(y^{\prime}) = -27x^3(y^{\prime})$.
The highest order derivative present is $y^{\prime \prime}$,so the order $a = 2$.
The highest power of the highest order derivative after making the equation a polynomial in derivatives is $2 \times 3 = 6$. Thus,the degree $b = 6$.
Comparing $a = 2$ and $b = 6$,we get $b = 3a$.
142
EasyMCQ
The order and degree of the differential equation $\sqrt{\frac{dy}{dx}} - 4\frac{dy}{dx} - 7x = 0$ are respectively:
A
$1$ and $\frac{1}{2}$
B
$2$ and $1$
C
$1$ and $1$
D
$1$ and $2$

Solution

(D) Given differential equation is $\sqrt{\frac{dy}{dx}} - 4\frac{dy}{dx} - 7x = 0$.
Rearranging the terms,we get $\sqrt{\frac{dy}{dx}} = 4\frac{dy}{dx} + 7x$.
Squaring both sides to remove the radical sign,we get:
$\frac{dy}{dx} = (4\frac{dy}{dx} + 7x)^2$
$\frac{dy}{dx} = 16(\frac{dy}{dx})^2 + 49x^2 + 56x\frac{dy}{dx}$.
The highest order derivative present is $\frac{dy}{dx}$,so the order is $1$.
The exponent of the highest order derivative after making the equation a polynomial in derivatives is $2$,so the degree is $2$.
Thus,the order is $1$ and the degree is $2$.
143
EasyMCQ
If $c_1, c_2, c_3, c_4, c_5$ are arbitrary constants,then the order of the differential equation whose general solution is $y=(c_1+c_2) \sin (x+c_3)+c_4 e^{x+c_5}$ is
A
$3$
B
$5$
C
$4$
D
Not defined

Solution

(A) The given general solution is $y=(c_1+c_2) \sin (x+c_3)+c_4 e^{x+c_5}$.
We can simplify the expression by substituting constants:
Let $A = c_1+c_2$ and $B = c_4 e^{c_5}$.
Then the equation becomes $y = A \sin (x+c_3) + B e^x$.
Using the trigonometric identity $\sin (x+c_3) = \sin x \cos c_3 + \cos x \sin c_3$,we get:
$y = A (\sin x \cos c_3 + \cos x \sin c_3) + B e^x$
$y = (A \cos c_3) \sin x + (A \sin c_3) \cos x + B e^x$.
Let $K_1 = A \cos c_3$,$K_2 = A \sin c_3$,and $K_3 = B$.
Thus,$y = K_1 \sin x + K_2 \cos x + K_3 e^x$.
There are $3$ essential arbitrary constants $(K_1, K_2, K_3)$.
The order of a differential equation is equal to the number of essential arbitrary constants in its general solution.
Therefore,the order of the differential equation is $3$.
144
EasyMCQ
The product of the degree and order of the differential equation $\left(\frac{d^2 y}{d x^2}\right)^2-\left(\frac{d y}{d x}\right)^3=y^3$ is
A
$3$
B
$4$
C
$6$
D
$5$

Solution

(B) The given differential equation is $\left(\frac{d^2 y}{d x^2}\right)^2-\left(\frac{d y}{d x}\right)^3=y^3$.
The order of a differential equation is the order of the highest derivative present in the equation. Here,the highest derivative is $\frac{d^2 y}{d x^2}$,so the order is $2$.
The degree of a differential equation is the power of the highest derivative when the equation is expressed as a polynomial in derivatives. Here,the power of $\frac{d^2 y}{d x^2}$ is $2$,so the degree is $2$.
The product of the degree and the order is $2 \times 2 = 4$.
145
EasyMCQ
Find the sum of the order and degree of the differential equation $y = x(\frac{dy}{dx})^3 + \frac{d^2y}{dx^2}$.
A
$2$
B
$3$
C
$4$
D
$5$

Solution

(B) The given differential equation is $y = x(\frac{dy}{dx})^3 + \frac{d^2y}{dx^2}$.
The order of a differential equation is the order of the highest derivative present in the equation. Here,the highest derivative is $\frac{d^2y}{dx^2}$,so the order is $2$.
The degree of a differential equation is the power of the highest derivative when the equation is expressed as a polynomial in derivatives. Here,the power of the highest derivative $\frac{d^2y}{dx^2}$ is $1$.
Thus,the order is $2$ and the degree is $1$.
The sum of the order and degree is $2 + 1 = 3$.
Therefore,option $(B)$ is correct.
146
EasyMCQ
Find the degree of the differential equation $y_3^{2/3} + 2 + 3y_2 + y_1 = 0$.
A
$4$
B
$2$
C
$3$
D
$1$

Solution

(B) The given differential equation is $y_3^{2/3} + 2 + 3y_2 + y_1 = 0$.
To find the degree,we must first eliminate the fractional exponent of the highest order derivative.
Rearranging the equation,we get $y_3^{2/3} = -(2 + 3y_2 + y_1)$.
Cubing both sides to remove the fractional power,we obtain $(y_3^{2/3})^3 = (-(2 + 3y_2 + y_1))^3$,which simplifies to $y_3^2 = -(2 + 3y_2 + y_1)^3$.
The highest order derivative present is $y_3$ (the third derivative),and its exponent after rationalizing the equation is $2$.
Therefore,the degree of the differential equation is $2$.
Hence,option $B$ is correct.
147
MediumMCQ
The order and the degree of the differential equation $y=px+\sqrt{a^2p^2+b^2}$,(where $p=\frac{dy}{dx}$) are respectively.
A
$2, 1$
B
$1, 2$
C
$1, 1$
D
$2, 2$

Solution

(B) Given the differential equation:
$y = px + \sqrt{a^2p^2 + b^2}$,where $p = \frac{dy}{dx}$.
To find the order and degree,we first eliminate the square root by squaring both sides:
$\sqrt{a^2p^2 + b^2} = y - px$
Squaring both sides:
$a^2p^2 + b^2 = (y - px)^2$
$a^2p^2 + b^2 = y^2 + p^2x^2 - 2xyp$
Rearranging the terms:
$(x^2 - a^2)p^2 - 2xyp + (y^2 - b^2) = 0$
Substituting $p = \frac{dy}{dx}$:
$(x^2 - a^2)\left(\frac{dy}{dx}\right)^2 - 2xy\left(\frac{dy}{dx}\right) + (y^2 - b^2) = 0$
The highest order derivative present is $\frac{dy}{dx}$,so the order is $1$.
The highest power of the highest order derivative is $2$,so the degree is $2$.
Thus,the order and degree are $1$ and $2$ respectively.
148
EasyMCQ
The order and degree of the differential equation $\frac{dy}{dx} = \left(\frac{d^2y}{dx^2} + 2\right)^{1/2} + \frac{d^2y}{dx^2} + 5$ are respectively
A
$2, 1$
B
$2, 4$
C
$2, 2$
D
$2, 3$

Solution

(C) Given equation: $\frac{dy}{dx} = \left(\frac{d^2y}{dx^2} + 2\right)^{1/2} + \frac{d^2y}{dx^2} + 5$
Rearranging the terms to isolate the radical: $\frac{dy}{dx} - \frac{d^2y}{dx^2} - 5 = \left(\frac{d^2y}{dx^2} + 2\right)^{1/2}$
Squaring both sides: $\left(\frac{dy}{dx} - \frac{d^2y}{dx^2} - 5\right)^2 = \frac{d^2y}{dx^2} + 2$
Expanding the left side: $\left(\frac{dy}{dx}\right)^2 + \left(\frac{d^2y}{dx^2}\right)^2 + 25 - 2\frac{dy}{dx}\frac{d^2y}{dx^2} - 10\frac{dy}{dx} + 10\frac{d^2y}{dx^2} = \frac{d^2y}{dx^2} + 2$
Simplifying the equation: $\left(\frac{d^2y}{dx^2}\right)^2 + \left(\frac{dy}{dx}\right)^2 - 2\frac{dy}{dx}\frac{d^2y}{dx^2} - 10\frac{dy}{dx} + 9\frac{d^2y}{dx^2} + 23 = 0$
The highest order derivative present is $\frac{d^2y}{dx^2}$,so the order is $2$.
The highest power of the highest order derivative is $2$,so the degree is $2$.
149
EasyMCQ
The degree and order of the differential equation of the family of parabolas whose axis is the $X$-axis,are respectively
A
$2$,$2$
B
$2$,$1$
C
$1$,$2$
D
$3$,$2$

Solution

(C) The equation of the family of parabolas with the $X$-axis as their axis is given by $y^2 = 4a(x - b)$,where $a$ and $b$ are arbitrary constants.
To eliminate these two constants,we differentiate with respect to $x$:
$2y \frac{dy}{dx} = 4a \implies y \frac{dy}{dx} = 2a$.
Differentiating again with respect to $x$:
$y \frac{d^2y}{dx^2} + \left(\frac{dy}{dx}\right)^2 = 0$.
The highest order derivative present is $\frac{d^2y}{dx^2}$,so the order is $2$.
The power of the highest order derivative is $1$,so the degree is $1$.
Thus,the degree and order are $1$ and $2$ respectively.

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