Question:
The sum
$\frac{3 \times 1^{3}}{1^{2}}+\frac{5 \times\left(1^{3}+2^{3}\right)}{1^{2}+2^{2}}+\frac{7 \times\left(1^{3}+2^{3}+3^{3}\right)}{1^{2}+2^{2}+3^{2}}+\ldots \ldots .$
Correct Option: 1
Solution:
$\mathrm{T}_{\mathrm{n}}=\frac{(3+(\mathrm{n}-1) \times 2)\left(\mathrm{l}^{3}+2^{3}+\ldots+\mathrm{n}^{3}\right)}{\left(1^{2}+2^{2}+\ldots+\mathrm{n}^{2}\right)}$
$=\frac{3}{2} n(n+1)=\frac{n(n+1)(n+2)-(n-1) n(n+1)}{2}$
$\Rightarrow S_{n}=\frac{n(n+1)(n+2)}{2}$
$\Rightarrow S_{10}=660$
Click here to get exam-ready with eSaral
For making your preparation journey smoother of JEE, NEET and Class 8 to 10, grab our app now.