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Question

Mathematics Question on limits and derivatives

limn\displaystyle \lim_{n \to \infty} (1n2+3n2+5n2+.....+2n+1n2)\left(\frac{1}{n^{2}}+\frac{3}{n^{2}}+\frac{5}{n^{2}}+.....+\frac{2n+1}{n^{2}}\right) is equal to

A

12\frac{1}{2}

B

11

C

12-\frac{1}{2}

D

1-1

Answer

11

Explanation

Solution

limn\displaystyle \lim_{n \to \infty} (1n2+3n2+5n2+.......+2n+1n2)\left(\frac{1}{n^{2}}+\frac{3}{n^{2}}+\frac{5}{n^{2}}+.......+\frac{2n+1}{n^{2}}\right) =limn=\displaystyle \lim_{n \to \infty} 1n2(1+3+5+.......+(2n+1))\frac{1}{n^{2}}\left(1+3+5+.......+\left(2n+1\right)\right) =limn=\displaystyle \lim_{n \to \infty} (n+1)2n2\frac{\left(n+1\right)^{2}}{n^{2}} =limn=\displaystyle \lim_{n \to \infty} n2+1+2nn2\frac{n^{2}+1+2n}{n^{2}} =limn=\displaystyle \lim_{n \to \infty} (1+1n2+2n)=1\left(1+\frac{1}{n^{2}}+\frac{2}{n}\right)=1