d, $\dfrac{5x+10}{4x-8}.\dfrac{4-2x}{x+2}$ ĐKXĐ: $x\neq±2$
$=\dfrac{5(x+2)}{4(x-2)}.\dfrac{-2(x-2)}{x+2}$
$=\dfrac{-10}{4}$
$=\dfrac{-5}{2}$
Bài 2:
a, $\dfrac{6x^2y^3}{8x^3y^2}=\dfrac{3y}{4x}$ ($x;y\neq0$)
b, $\dfrac{x^3-x}{3x+3}=\dfrac{x(x^2-1)}{3(x+1)}=\dfrac{x(x-1)(x+1)}{3(x+1)}=\dfrac{x(x-1)}{3}$ ($x\neq-1$)
c, $\dfrac{x^2+3xy}{x^2-9y^2}$ ($x\neq±3y$)
$=\dfrac{x(x+3y)}{(x-3y)(x+3y)}$
$=\dfrac{x}{x-3y}$
d, $\dfrac{x^2+4x+4}{3x+6}=\dfrac{(x+2)^2}{3(x+2)}=\dfrac{x+2}{3}$ ($x\neq-2$).
