........ also mentioned a method to find the solution of quadratic equation.

The speed of a motorboat in still water is $25 \text{ km/hr}$. In a river, it covers $60 \text{ km}$ downstream and the same distance upstream in a total time of $5 \text{ hours}$. Find the speed of the current of the river. (The speed of the current of the river is less than the speed of the motorboat in still water.) (in $\text{ km/hr}$)

Obtain the roots of the following quadratic equation by using the quadratic formula: $6x^{2} + x - 2 = 0$.

Solve the following equation using the method of factorization and write its solution set: $\frac{x+1}{x+2} + \frac{1}{x} = \frac{5}{4}$

If $b=0$ and $c < 0$,is it true that the roots of $x^{2}+bx+c=0$ are numerically equal and opposite in sign? Justify.

The formula for finding the value of $D$ (discriminant) for a quadratic equation $ax^2 + bx + c = 0$ is $\ldots \ldots \ldots \ldots.$