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Need solution for RD Sharma Maths Class 12 Chapter 18 Indefinite Integrals Excercise 18.30 Question 32

Answers (1)

Answer:

            \frac{1}{x+1}+\log |x+2|+C

Hint:

            To solve this integration, we use partial fraction method   

Given:

            \int \frac{x^{2}+x-1}{(x+1)^{2}(x+2)} d x \\

Explanation:

Let

\begin{aligned} &I=\int \frac{x^{2}+x-1}{(x+1)^{2}(x+2)} d x \\ &\frac{x^{2}+x-1}{(x+1)^{2}(x+2)}=\frac{A}{x+1}+\frac{B}{(x+1)^{2}}+\frac{C}{x+2} \\ &x^{2}+x-1=A(x+1)(x+2)+B(x+2)+C(x+1)^{2} \\ &x^{2}+x-1=(A+C) x^{2}+(3 A+B+2 C) x+(2 A+2 B+C) \end{aligned}

Equating the similar terms

\begin{aligned} &A+C=1 \\ &3 A+B+2 C=1 \\ &2 A+2 B+C=-1 \end{aligned}

On solving we get

A=0 ,B=-1, C=1

Thus

\begin{aligned} &\frac{x^{2}+x-1}{(x+1)^{2}(x+2)}=\frac{0}{x+1}+\frac{(-1)}{(x+1)^{2}}+\frac{1}{x+2} \\ &I=\int \frac{-1}{(x+1)^{2}} x+\int \frac{1}{x+2} d x \\ &I=\frac{1}{x+1}+\log |x+2|+C \end{aligned}

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