已知x+y=2,xy=2,求1/2x3y+x2y2+1/2xy3的值.

问题描述:

已知x+y=2,xy=2,求

1
2
x3y+x2y2+
1
2
xy3的值.

1
2
x3y+x2y2+
1
2
xy3
=
1
2
xy(x2+2xy+y2),
=
1
2
xy(x+y)2
当x+y=2,xy=2时,原式=
1
2
×2×22=4.