Quy đồng mẫu thức các phân thức sau

`a)`

$\dfrac{3x+6}{x^2-4}$`=`$\dfrac{3x+6}{(x+2)(x-2)}$`=`$\dfrac{3x+6}{(x+2)(x-2)}$

$\dfrac{5x}{x^2-2x}$`=`$\dfrac{5x}{x(x-2)}$`=`$\dfrac{5(x+2)}{(x+2)(x-2)}$

$\dfrac{1-x}{x^2-3x+2}$`=`$\dfrac{1-x}{(x-2)(x-1)}$`=`$\dfrac{-1}{x-2}$`=`$\dfrac{-(x+2)}{(x+2)(x-2)}$

`b)`

$\dfrac{1}{3x+3y}$`=`$\dfrac{1}{3(x+y)}$`=`$\dfrac{2(x+y)}{6(x+y)^2}$

$\dfrac{1}{2x+2y}$`=`$\dfrac{1}{2(x+y)}$`=`$\dfrac{3(x+y)}{6(x+y)^2}$

$\dfrac{1}{x^2+2xy+y^2}$`=`$\dfrac{1}{(x+y)^2}$`=`$\dfrac{6}{6(x+y)^2}$

`c)`

$\dfrac{4x^2-3x+5}{x^3-1}$`=`$\dfrac{4x^2-3x+5}{(x-1)(x^2+x+1)}$

$\dfrac{2x}{x^2+x+1}$`=`$\dfrac{2x(x-1)}{(x-1)(x^2+x+1)}$

$\dfrac{6}{x-1}$`=`$\dfrac{6(x^2+x+1)}{(x-1)(x^2+x+1)}$

`d)`

$\dfrac{7}{5x}$`=`$\dfrac{7(x+2y)(x-2y)}{5x(x-2y)(x+2y)}$`=`$\dfrac{14(x+2y)(x-2y)}{10x(x+2y)(x-2y)}$

$\dfrac{4}{x-2y}$`=`$\dfrac{4.5x}{5x.(x-2y)}$`=`$\dfrac{40x(x+2y)}{10x(x+2y)(x-2y)}$

$\dfrac{x-y}{8y^2-2x^2}$`=`$\dfrac{y-x}{2(x-2y)(x+2y)}$`=`$\dfrac{5x(y-x)}{10x(x-2y)(x+2y)}$