A calculus problem by Shourya Pandey

Calculus Level 4

lim n ( n n + 1 e ( n + 1 ) n n ) = ? \large\displaystyle \lim_{n\to\infty} \left(\dfrac {n^{n+1}e}{(n+1)^n} - n\right) = \, ? Clarification : e e denotes Euler's number , e 2.71828 e \approx 2.71828 .

e e 0.25 0.25 0.5 0.5 e 2 e^2

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2 solutions

Rudraksh Shukla
May 3, 2016

I am a little short on time so i will just give a quick insight to what I did. Take the LCM of the expression lim n n n + 1 e n ( n + 1 ) n ( n + 1 ) n \lim_{n \to\infty} \dfrac{n^{n+1}e-n(n+1)^n}{(n+1)^n} Divide numerator and denominator by n n + 1 n^{n+1} , lim n e ( 1 + 1 n ) n 1 n ( 1 + 1 n ) n \lim_{n \to\infty} \dfrac{e-(1+\frac{1}{n})^n}{\frac{1}{n}(1+\frac{1}{n})^n} Substitute 1 n = x \frac{1}{n}=x and change the limit as, lim x 0 e ( 1 + x ) 1 x x ( 1 + x ) 1 x \lim_{x\to 0} \dfrac{e-(1+x)^{\frac{1}{x}}}{x(1+x)^{\frac{1}{x}}} Now since lim x 0 ( 1 + x ) 1 x = e \lim_{x \to 0} (1+x)^{\frac{1}{x}} =e therefore we have the 0 0 \frac{0}{0} form which can be easily analyzed with L Hopitals rule. One formula which you may use while applying L Hopitals rule is lim x 0 l n ( 1 + x ) x = 1 \lim_{x\to 0} \dfrac{ln(1+x)}{x}=1

Something is wrong.

When you substituted 1/n=x, you can't say it directly that Limit will change to tending to zero.Correct thing would that limit will,after substitution,tend to 0 + 0^{+}

Harsh Shrivastava - 3 years, 11 months ago

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The solution is wrong. Correct answer is zero , which is not in option.

Reetun Maiti - 3 years, 4 months ago

I tried everything but answer is coming zero everytime

Sam Andrews - 2 years, 3 months ago

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