当x+y=-3,求(2x2+xy+3y2)-(x2-xy+2y2)的值,速求!

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当x+y=-3,求(2x2+xy+3y2)-(x2-xy+2y2)的值,速求!
当x+y=-3,求(2x2+xy+3y2)-(x2-xy+2y2)的值,速求!

当x+y=-3,求(2x2+xy+3y2)-(x2-xy+2y2)的值,速求!
(2x2+xy+3y2)-(x2-xy+2y2)
=2x²+xy+3y²-x²+xy-2y²
=x²+2xy+y²
=(x+y)²
=(-3)²
=9

（2x2+xy+3y2)-(x2-xy+2y2）
=x²+2xy+y²
=（x+y）²
=9