已知x+y=2,xy=1/2,求x3y-2x2y2+xy3的值.

问题描述:

已知x+y=2,xy=

1
2
,求x3y-2x2y2+xy3的值.

原式=xy(x2-2xy+y2
=xy[(x+y)2-4xy]
=

1
2
(22−4×
1
2
)
=1.