If $∫\frac{2x}{x^2+3x+2}dx=m log |x+2|+n log |x+1|+C, $ then the values of m and n are : |
$m=4, n=-2$ $m=-2, n=4$ $m=2, n=2$ $m=6, n=4$ |
$m=4, n=-2$ |
The correct answer is Option (1) → $m=4, n=-2$ $∫\frac{2x}{x^2+3x+2}dx=∫\frac{2x+3}{x^2+3x+2}-\frac{3}{x^2+3x+2}dx$ $⇒\log|x^2+3x+2|-3∫\frac{1}{(x+2)(x+1)}dx$ $⇒\log|x^2+3x+2|-3∫\frac{1}{1+x}-\frac{1}{x+2}dx$ as $\frac{1}{(x+2)(x+1)}=\frac{(x+2)-(x+1)}{(x+2)(x+1)}=\frac{1}{1+x}-\frac{1}{x+2}$ $\log(x+2)(x+1)-3\log(1+x)+3\log(2+x)+C$ $=\log(x+2)+3\log(x+2)+\log(x+1)-3\log(x+1)+C$ $4\log(x+2)-2\log(x+1)+C$ $m=4,n=-2$ |