$\int \frac{x+1}{x^{2}+5 x+6} d x=$

$\int \frac{x+1}{x^{2}+5 x+6} d x=$
  1. $-\log |x+2|-2 \log |x+3|+C$
  2. $-\log |x+2|+2 \log |x+3|+C$
  3. $2 \log |x+2|-2 \log |x+3|+C$
  4. $\log |x+2|+2 \log |x+3|+C$

Solution

$I=\int \frac{x+1}{x^{2}+5 x+6} d x$ Let $\quad \frac{x+1}{(x+3)(x+2)}=\int\left[\frac{x+1}{(x+3)(x+2)}\right] d x$ $\therefore x+1=A(x+2)+B(x+3)$ When $x=-2$, we get $B=-1$ When $x=-3$, we get $A=2$ $\therefore I=\int\left[\frac{2}{x+3}-\frac{B}{x+2}\right] d x$ $\therefore 2 \log |(x+3)|-\log |x+2|+c$

Asked in: MHT CET 2020 (20 Oct Shift 1)

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