已知x-y=-1,xy=3.求x^3y-2x^2y^2+xy^3的值快

问题描述:

已知x-y=-1,xy=3.求x^3y-2x^2y^2+xy^3的值

x^3y-2x^2y^2+xy^3
=xy(x²-2xy+y²)
=xy(x-y)²
=3(-1)²
=3