36x²y-48xy=12xy(3x-4y)
y(x-y)²-(y-x)³=y(x-y)²+(x-y)³=(x-y)^2(y+x-y)=x(x-y)^2
3ax²+6axy+3ay²=3a(x^2+2xy+y^2)=3a(x+y)^2