làm vớ vẩn + spam = méc mod Thực hiện phép nhân phân thức đại số Bài 1 : d) 2x^2/x-y . y/5x^3 g) x^2 – 9y^2/x^2y^2 . 3xy/ 2x – 6y h) 3x^2 – 3y^2 /5xy

d,

$\dfrac{2x^2}{x-y}.\dfrac{y}{5x^3}$

$=\dfrac{2x^2y}{5x^3(x-y)}$

$=\dfrac{2y}{5x(x-y)}$

g,

$\dfrac{x^2-9y^2}{x^2y^2}.\dfrac{3xy}{2x-6y}$

$=\dfrac{(x^2-(3y)^2).3xy}{(xy)^2.2(x-3y)}$

$=\dfrac{(x-3y)(x+3y).3}{xy.2(x-3y)}$

$=\dfrac{3(x+3y)}{2xy}$

h,

$\dfrac{3x^2-3y^2}{5xy}.\dfrac{15x^2y}{2y-2x}$

$=\dfrac{3(x-y)(x+y).15x^2y}{-5xy.2(x-y)}$

$=\dfrac{3(x+y).3x}{-2}$

$=\dfrac{-9x(x+y)}{2}$

i,

$\dfrac{2a^3-2b^3}{3a+3b}.\dfrac{6a+6b}{a^2-2ab+b^2}$

$=\dfrac{2(a-b)(a^2+ab+b^2).6(a+b)}{3(a+b).(a-b)^2}$

$=\dfrac{4(a^2+ab+b^2)}{a-b}$