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The value of $$\displaystyle \lim_{n \to \infty} \left[ (n+1) \int_0^1 x^n \ln(1+x) dx \right]$$ is

  1. $0$
  2. $\ln 2$
  3. $\ln 3$
  4. $\infty$
in Calculus by Veteran (432k points)
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1 Answer

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Answer: $B$

$$\underset{n \to \infty}{\lim} \int^1_0x^n\ln(1+x)dx$$

can be simplified to:

$$\ln(2)-\underset{n \to \infty}{\lim}\int^1_0\frac{x^{n+1}}{1 + x}dx$$

$$\because \bigg |\int^1_0\frac{x^{n+1}}{1+x}dx\bigg | \le \int^1_0 \big |x^{n+1} \big|dx$$

Now, here the bound $1+x$ is always greater than equal to $1$

$\Rightarrow \frac{1}{1+x} \le1$

$$\therefore \underset{n \to \infty}{\lim}\int^1_0 x^n \ln(1+x)dx = \ln(2)$$

Thus, $B$ be is the correct option.

by Boss (19.2k points)

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