已知x-2y=-2,xy=8,求x^3y-4x^2y^2+4xy^3,求值.
问题描述:
已知x-2y=-2,xy=8,求x^3y-4x^2y^2+4xy^3,求值.
答
x^3y-4x^2y^2+4xy^3
=xy(x^2-4xy+4y^2)
=xy(x-2y)^2
=8×(-2)^2
=32