已知x+y=-3,求(2x^2+xy+3y^2)-(x^2-xy+2y^2)的值.

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已知x+y=-3,求(2x^2+xy+3y^2)-(x^2-xy+2y^2)的值.
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已知x+y=-3,求(2x^2+xy+3y^2)-(x^2-xy+2y^2)的值.
已知x+y=-3,求(2x^2+xy+3y^2)-(x^2-xy+2y^2)的值.

已知x+y=-3,求(2x^2+xy+3y^2)-(x^2-xy+2y^2)的值.
(2x^2+xy+3y^2)-(x^2-xy+2y^2)
=2x^2+xy+3y^2-x^2+xy-2y^2
=x^2+2xy+y^2
=(x+y)^2
=(-3)^2
=9

(2x^2+xy+3y^2)-(x^2-xy+2y^2)=2x^2+xy+3y^2-x^2+xy-2y^2=x^2+2xy+y^2
=(x+y)^2=(-3)^2=9

9