1)

$\frac{d}{dx}\left(\frac{x+5}{(x+1)^{2}(x+2)}\right)=$


A) $\frac{8}{(x+2)^{2}}-\frac{3}{(x+1)^{2}}+\frac{3}{(x+1)^{3}}$

B) $\frac{3}{(x+1)^{2}}-\frac{3}{(x+2)^{2}}-\frac{8}{(x+1)^{3}}$

C) $\frac{3}{(x+2)^{2}}-\frac{3}{(x+1)^{3}}-\frac{8}{(x+1)^{2}}$

D) $\frac{8}{(x+2)^{2}}-\frac{3}{(x+1)^{3}}+\frac{3}{(x+1)^{2}}$

Answer:

Option B

Explanation:

$\frac{x+5}{(x+1)^{2}(x+2)}=\frac{A}{(x+1)^{}}+\frac{B}{(x+1)^{2}}+\frac{C}{(x+2)^{}}$  ..........(i)

$\Rightarrow$     $x+5= A(x+1)(x+2)+B(x+2)+c(x+1)^{2}$

$\Rightarrow$   $x+5= x^{2}(A+C)+x(3A+B+2C)+2A+2B+C$

on comparing  the coefficients of like power of x , we get

 $A+C=0$,

 $3A+B+2C=1$  and $2A+2B+C=5$

 on substituting  A=-C  in last two equations, we get

    B-C=1  .....(ii)

    and  2B-C=5   .......(iii)

 On subtracting Eqs(ii) and (iii) , we get

              $B=4 \Rightarrow C=3$      [from Eq.(ii)]

and hence     A=-3

 Now,    $\frac{x+5}{(x+1)^{2}(x+2)}=\frac{-3}{(x+1)^{}}+\frac{4}{(x+1)^{2}}+\frac{3}{(x+2)^{}}$

On differentiating  both sides  w.r.t x, we get

$\frac{d}{dx}\left(\frac{x+5}{(x+1)^{2}(x+2)}\right)=$   $\frac{3}{(x+1)^{2}}-\frac{8}{(x+1)^{3}}-\frac{3}{(x+2)^{2}}$