已知x²+xy=3,xy+y²=—2,求x²-y²的值?x²+4xy+3y²的值?2x²-xy-3y
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![已知x²+xy=3,xy+y²=—2,求x²-y²的值?x²+4xy+3y²的值?2x²-xy-3y](/uploads/image/z/7627927-31-7.jpg?t=%E5%B7%B2%E7%9F%A5x%26sup2%3B%2Bxy%3D3%2Cxy%2By%26sup2%3B%3D%E2%80%942%2C%E6%B1%82x%26sup2%3B-y%26sup2%3B%E7%9A%84%E5%80%BC%3Fx%26sup2%3B%2B4xy%2B3y%26sup2%3B%E7%9A%84%E5%80%BC%3F2x%26sup2%3B-xy-3y)
已知x²+xy=3,xy+y²=—2,求x²-y²的值?x²+4xy+3y²的值?2x²-xy-3y
已知x²+xy=3,xy+y²=—2,求x²-y²的值?x²+4xy+3y²的值?2x²-xy-3y
已知x²+xy=3,xy+y²=—2,求x²-y²的值?x²+4xy+3y²的值?2x²-xy-3y
x²+xy=3,xy+y²=-2
相减
x²+xy-xy-y²=3+2
x²-y²=5
x²+xy=3(1)
xy+y²=-2 (2)
(2)*3+(1)
x²+xy+3xy+3y²=3-6
x²+4xy+3y²=-3
(1)*2-(2)*3
2x²+2xy-3xy-3y²=6+6
2x²-xy-3y²=12