Đáp án:
$=\dfrac{1}{x}$
Lời giải:
$\dfrac{3}{2x+6}-\dfrac{x-6}{2x^2+6x}$
$=\dfrac{3}{2.(x+3)}-\dfrac{x-6}{2x(x+3)}$
$=\dfrac{3x}{2x(x+3)}-\dfrac{x-6}{2x(x+3)}$
$=\dfrac{3x-x+6}{2x(x+3)}$
$=\dfrac{2x+6}{2x(x+3)}$
$=\dfrac{2(x+3)}{2x(x+3)}$
$=\dfrac{1}{x}$