The value of lim _{n} {rightarrow infty} left | vedclass

Name: Exam Paper Generator | JEE NEET Paper Generator | Vedclass
Brand: Vedclass
Rating: 5 (35 reviews)

Question

(A) The given expression can be written as $\lim _{n \rightarrow \infty} \sum_{r=0}^{n-1} \frac{\sqrt{n}}{\sqrt{(n+4 r)^{3}}}$.We can rewrite the sum

Vedclass · Accepted Answer

$\frac{5-\sqrt{5}}{10}$

Vedclass · Answer

(A) The given expression can be written as $\lim _{n \rightarrow \infty} \sum_{r=0}^{n-1} \frac{\sqrt{n}}{\sqrt{(n+4 r)^{3}}}$.We can rewrite the sum as $\sum_{r=0}^{n-1} \frac{1}{n} \left( \frac{n \sqrt{n}}{\sqrt{(n+4 r)^{3}}} \right) = \sum_{r=0}^{n-1} \frac{1}{n} \left( \frac{1}{(1+\frac{4 r}{n})^{3 / 2}} \right)$.This is a Riemann sum which converges to the definite integral $\int_{0}^{1} \frac{dx}{(1+4x)^{3/2}}$.Let $z = 1+4x$, then $dz = 4dx$, so $dx = \frac{dz}{4}$.When $x=0, z=1$ and when $x=1, z=5$.The integral becomes $\frac{1}{4} \int_{1}^{5} z^{-3/2} dz = \frac{1}{4} \left[ \frac{z^{-1/2}}{-1/2} \right]_{1}^{5} = -\frac{1}{2} \left[ \frac{1}{\sqrt{z}} \right]_{1}^{5}$.$= -\frac{1}{2} \left( \frac{1}{\sqrt{5}} - 1 \right) = \frac{1}{2} \left( 1 - \frac{1}{\sqrt{5}} \right) = \frac{\sqrt{5}-1}{2\sqrt{5}} = \frac{5-\sqrt{5}}{10}$.

The value of $\lim _{n}$ ${\rightarrow \infty} \left( \frac{\sqrt{n}}{\sqrt{n^{3}}}+\frac{\sqrt{n}}{\sqrt{(n+4)^{3}}}+\frac{\sqrt{n}}{\sqrt{(n+8)^{3}}}+\cdots +\frac{\sqrt{n}}{\sqrt{[n+4(n-1)]^{3}}} \right)$ is

Similar Questions

Let $S_n = \sum_{k=1}^n \frac{n}{n^2+kn+k^2}$ and $T_n = \sum_{k=0}^{n-1} \frac{n}{n^2+kn+k^2}$ for $n=1, 2, 3, \ldots$. Then,

$\lim _{n}$ ${\rightarrow \infty}\left(\frac{1}{1+n^5}+\frac{2^4}{2^5+n^5}+\frac{3^4}{3^5+n^5}+\ldots+\frac{n^4}{n^5+n^5}\right)=$

$\lim _{n \rightarrow \infty}\left[\left(1+\frac{1}{n^3}\right)^{\frac{1}{n^3}}\left(1+\frac{8}{n^3}\right)^{\frac{4}{n^3}}\left(1+\frac{27}{n^3}\right)^{\frac{9}{n^3}} \ldots \left(1+\frac{n^3}{n^3}\right)^{\frac{n^2}{n^3}}\right]=$

If $\mathop {\lim }\limits_{n \to \infty } \frac{{{1^a} + {2^a} + \dots + {n^a}}}{{{{\left( {n + 1} \right)}^{a - 1}}\left[ {\left( {na + 1} \right) + \dots + \left( {na + n} \right)} \right]}} = \frac{1}{{60}}$ for some positive real number $a$,then $a$ is equal to

$\mathop {\lim }\limits_{n \to \infty } {\left( {\frac{{\left( {n + 1} \right)\left( {n + 2} \right) \ldots \left( {3n} \right)}}{{{n^{2n}}}}} \right)^{\frac{1}{n}}} = $

Vedclass Test Series

Exam Paper Generator

Online Exam Module