$\begin{aligned} & \text { If } \frac{3 x^2+1}{\left(x^2+1\right)\left(x^2+2\right)^2}=\frac{A…

$\begin{aligned} & \text { If } \frac{3 x^2+1}{\left(x^2+1\right)\left(x^2+2\right)^2}=\frac{A x+B}{x^2+1}+\frac{C x+D}{x^2+2} \\ & +\frac{E x+F}{\left(x^2+2\right)^2}, \text { then } A+C+E=\end{aligned}$
  1. 0
  2. $\frac{7}{3}$
  3. 1
  4. $\frac{4}{3}$

Solution

If $ \begin{array}{r} \frac{3 x^2+1}{\left(x^2+1\right)\left(x^2+2\right)^2}=\frac{A x+B}{x^2+1}+\frac{C x+D}{x^2+2}+\frac{E x+F}{\left(x^2+2\right)^2} \\ \Rightarrow \frac{3 x^2+1}{\left(x^2+1\right)\left(x^2+2\right)^2} \\ \end{array} $ $\begin{aligned} & A x+B\left(x^2+2\right)^2+(C x+D)\left(x^2+1\right) \\ = & \frac{\left(x^2+2\right)+(E x+F)\left(x^2+1\right)}{\left(x^2+1\right)\left(x^2+2\right)^2}\end{aligned}$ $ \begin{gathered} \Rightarrow \quad 3 x^2+1=(A x+B)\left(x^2+2\right)^2+(C x+D) \\ \left(x^2+1\right)\left(x^2+2\right)+(E x+F)\left(x^2+1\right) \end{gathered} $ On comparing the coefficient of different term, $A=0, C=0$ and $E=0$ So, $ A+C+E=0 $

Asked in: AP EAMCET 2018 (22 Apr Shift 2)

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