Đáp án:
$A = (\dfrac{1}{x^2 + x} - \dfrac{2 - x}{x + 1}) : (\dfrac{1}{x} + x - 2)$
$A = \dfrac{1}{x(x + 1)} + \dfrac{x - 2}{x + 1}) : (\dfrac{1 + x^2 - 2x}{x})$
$A = \dfrac{1 + x(x + 2)}{x(x + 1} : \dfrac{(x- 1)^2}{x}$
$A = \dfrac{x^2 + 2x + 1}{x(x + 1)} . \dfrac{x}{(x - 1)^2}$
$A = \dfrac{(x + 1)^2}{x(x + 1)} . \dfrac{x}{(x - 1)^2} = \dfrac{x + 1}{(x - 1)^2}$
$B = \dfrac{3}{2x + 6} + \dfrac{x - 6}{2x^2 + 6x}$
$B = \dfrac{3}{2(x + 3)} - \dfrac{x - 6}{2x(x + 3)}$
$B = \dfrac{3.x}{2x(x + 3)} - \dfrac{x - 6}{2x(x + 3)}$
$B = \dfrac{3x - x + 6}{2x(x + 3)} = \dfrac{2x + 6}{2x(x + 3)}$
$B = \dfrac{2(x + 3)}{2x(x + 3)} = \dfrac{1}{x}$
Giải thích các bước giải:
