已知x+y=1,则1/2x2+xy+1/2y2=_.

问题描述:

已知x+y=1,则

1
2
x2+xy+
1
2
y2=______.

∵x+y=1,

1
2
x2+xy+
1
2
y2
=
1
2
(x2+2xy+y2),
=
1
2
(x+y)2
=
1
2