1、1/4x^2-xy+y^2=(1/4)*(x²-4xy+4y²）=(1/4)*(x-2y)²2、36x^2y-48xy^2=12xy(3x-4y)3、y(x-y)^2-(y-x)^3=y(x-y)^2 +(x-y)^3=(y+x-y)(x-y)²=x(x-y)²4、-x^2y^2+z^2=z²-x²y²=(z+xy)(z-xy)
