已知x+y=1,求1/2x²+xy+1/2y²的值

问题描述:

已知x+y=1,求1/2x²+xy+1/2y²的值

低估好
1/2x²+xy+1/2y²
=1/2(x²+2xy+y²)
=1/2(x+y)²
=1/2*1²
=1/2