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Explain Solution R.D.Sharma Class 12 Chapter 18 Indefinite Integrals Exercise Multiple Choice Questions  Question 34 Maths Textbook Solution.

Answers (1)

Answer:

x-\frac{x^{2}}{2}+\frac{x^{3}}{3}-\log |1+x|+C

Given:

\int \frac{x^{3}}{x+1} d x

Hint:

You must know how to integrate \int x^{n} d xand \int \frac{1}{x} d x

Explanation:

Let \mathrm{I}=\int \frac{x^{3}}{x+1} d x

         \begin{aligned} &=\int \frac{x^{3}+1-1}{x+1} d x \\ &=\int \frac{(x+1)\left(x^{2}+1-x\right)}{x+1} d x-\int \frac{1}{x+1} d x \end{aligned}                                                    \left[\because x^{3}+1=(x+1)\left(x^{2}+1-x\right)\right]

        \begin{aligned} &=\int\left(x^{2}+1-x\right) d x-\int \frac{1}{1+x} d x \\ &=\frac{x^{3}}{3}+x-\frac{x^{2}}{2}-\log |1+x|+C \\ &=x-\frac{x^{2}}{2}+\frac{x^{3}}{3}-\log |1+x|+C \end{aligned}

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