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How do I find $$\int\frac{2x^3 + 5x^2 +2x +2}{(x^2 +2x + 2)(x^2 + 2x - 2)}\mathrm dx$$

I used partial fractions by breaking up $x^2 + 2x - 2$ into $(x+1)^2 - 3$ and split it into $(a+b)(a-b)$ but as u can see it's extreme tedious. I was wondering if there is a faster technique to resolve this.

Ali Caglayan
  • 5,726
Danxe
  • 1,695

2 Answers2

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$$\int\frac{2x^3 + 5x^2 +2x +2}{(x^2 +2x + 2)(x^2 + 2x - 2)}\mathrm dx\\ =\int\left(+\frac{2x+2}{2(x^2+2x+2)}+\frac{2x+2}{2(x^2+2x-2)}-\frac1{\frac{(2x+2)^2}4+1}\right)\mathrm dx\\ =\frac12\ln(x^2+2x+2)+\frac12\ln(x^2+2x-2)-\arctan\left(\frac{2x+2}2\right)+\mathbb C$$

RE60K
  • 17,716
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HINT:

Write $$\frac{2x^3 + 5x^2 +2x +2)}{(x^2 +2x + 2)(x^2 + 2x - 2)}=\frac{Ax+B}{x^2+2x+2}+\frac{Cx+D}{x^2+2x-2}$$

For the ease of calculation, we can write

$$\frac{Ax+B}{x^2+2x+2}=\frac A2\cdot\frac{\left(\dfrac{d(x^2+2x+2)}{dx}\right)}{x^2+2x+2}+\frac C{(x+1)^2+1^2}.$$