Limit Sum

\hspace{-16}\displaystyle\mathbf{\lim_{n\rightarrow \infty}\frac{1}{\bold{\sqrt[2011]{n^{2011}+1}}}+\frac{1}{\bold{\sqrt[2011]{n^{2011}+2}}}+.......+\frac{1}{\bold{\sqrt[2011]{n^{2011}+n}}}}

11 Answers

1
johncenaiit ·

zero

21
Swaraj Dalmia ·

Taking n2011+ r ≈ n2011
Ans=1.

71
Vivek @ Born this Way ·

?

262
Aditya Bhutra ·

g(n) = \lim_{n\rightarrow \propto }\sum{} \frac{1}{\sqrt[2011]{n^{2011}+n}}

h(n) = \lim_{n\rightarrow \propto }\sum{} \frac{1}{\sqrt[2011]{n^{2011}+0}}

f(n) = \lim_{n\rightarrow \propto }\sum{} \frac{1}{\sqrt[2011]{n^{2011}+r}}

now

g(n)\leq f(n)\leq h(n)

it can easily be found the g(n)=h(n)=1

hence by sandwich theorem, f(n)=1

71
Vivek @ Born this Way ·

Thanks!

1
johncenaiit ·

how g(n)=h(n)=1?

i got it as 0...by dividing numerator and denominator by n...

pls help....

262
Aditya Bhutra ·

g(n) = \lim_{n\rightarrow \propto }\sum{} \frac{1}{\sqrt[2011]{n^{2011}+n}}

g(n) = \lim_{n\rightarrow \propto }\ \frac{n}{\sqrt[2011]{n^{2011}+n}}

dividing numerator and denominator by n ,

g(n) = \lim_{n\rightarrow \propto }\ \frac{1}{\sqrt[2011]{1+n^{-2011}}} =1

h(n) =1 in a similar way

1
johncenaiit ·

still confused....:(
how does the numerator in your second step become n??

262
Aditya Bhutra ·

since it is a summation of n like terms. (note the summation sign)

1
johncenaiit ·

ok ...i got that step.....

but what if i do the same thing directly in the question????
every term becomes zero

262
Aditya Bhutra ·

all the terms are infinitely small , but they are added infinitely many times to give a significant result.

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