已知x+y=-3,求(2x²+xy+3y²)-(x²-xy+2y²)的值.
问题描述:
已知x+y=-3,求(2x²+xy+3y²)-(x²-xy+2y²)的值.
²=平方
答
(2x²+xy+3y²)-(x²-xy+2y²)
=2x²+xy+3y²-x²+xy-2y²
=x²+2xy+y²
=(x+y)²
=9