The integral of $\frac{x^2-x}{x^3-x^2+x-1}$ w.r.t. $x$ is

The integral of $\frac{x^2-x}{x^3-x^2+x-1}$ w.r.t. $x$ is
  1. $\frac{1}{2} \log \left(x^2+1+c\right)$
  2. $\frac{1}{2} \log \left|x^2-1\right|+c$
  3. $\log \left(x^2+1+c\right)$
  4. $\log \left|x^2-1\right|+c$

Solution

Let $I=\int \frac{x^2-x}{x^3-x^2+x-1} d x$ $ =\int \frac{x(x-1)}{x^2(x-1)+(x-1)} d x=\int \frac{x d x}{x^2+1} $ $ \left.=\frac{1}{2} \int \frac{2 x d x}{\left(x^2+1\right.}\right) $ Let $x^2+1=t \Rightarrow 2 x d x=d t$ $ \begin{aligned} & \therefore I=\frac{1}{2} \int \frac{d t}{t}=\frac{1}{2} \log t+c \\ & =\frac{1}{2} \log \left(x^2+1\right)+c \end{aligned} $ where ' $c$ ' is the constant of integration

Asked in: JEE Main 2012 (12 May Online)

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