Functions Question 309

Question: $

[.] $ is equal to [IIT 1984; DCE 2000; Pb. CET 2000]

Options:

A) 0

B) $ -\frac{1}{2} $

C) $ \log ( \frac{2}{3} ) $

D) None of these

Show Answer

Answer:

Correct Answer: B

Solution:

$ \underset{n\to \infty }{\mathop{\lim }}[ \frac{1}{1-n^{2}}+\frac{2}{1-n^{2}}+…..+\frac{n}{1-n^{2}} ] $ $ =\underset{n\to \infty }{\mathop{\lim }}\frac{\Sigma n}{1-n^{2}}=\frac{1}{2}\underset{n\to \infty }{\mathop{\lim }}\frac{n^{2}+n}{1-n^{2}}=-\frac{1}{2} $ .