Let the sequence ${a_1},{a_2},{a_3},.............{a_{2n}}$ form an $A.P. $ Then $a_1^2 - a_2^2 + a_3^3 - ......... + a_{2n - 1}^2 - a_{2n}^2 = $
$\frac{n}{{2n - 1}}(a_1^2 - a_{2n}^2)$
$\frac{{2n}}{{n - 1}}(a_{2n}^2 - a_1^2)$
$\frac{n}{{n + 1}}(a_1^2 + a_{2n}^2)$
None of these
The sum of all natural numbers between $1$ and $100$ which are multiples of $3$ is
Let $a , b , c$ be in arithmetic progression. Let the centroid of the triangle with vertices $( a , c ),(2, b)$ and $(a, b)$ be $\left(\frac{10}{3}, \frac{7}{3}\right)$. If $\alpha, \beta$ are the roots of the equation $ax ^{2}+ bx +1=0$, then the value of $\alpha^{2}+\beta^{2}-\alpha \beta$ is ....... .
Three numbers are in $A.P.$ whose sum is $33$ and product is $792$, then the smallest number from these numbers is
If the sides of a right angled traingle are in $A.P.$, then the sides are proportional to
Let $a_n$ be a sequence such that $a_1 = 5$ and $a_{n+1} = a_n + (n -2)$ for all $n \in N$, then $a_{51}$ is