ab/(a+b)^2=ab (a-b)/(a+b)²(a-b)
b/a^2-b^2=b(a+b)/(a+b)²(a-b)
x/xy-y^2=x²/xy(x-y)
y/x^2-xy =y²/xy(x-y)我要最简公分母谢谢第一个最简公分母是(a+b)²(a-b)第二个最简公分母是xy(x-y)