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

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

人气：463 ℃　时间：2019-12-10 20:05:48

解答

（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