已知x²+xy=3,xy+y²=-2,求下列各式的值(1)x²-y²;(2)x²+4xy+3y²;(3)2x²-xy-3y²需要过程.
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![已知x²+xy=3,xy+y²=-2,求下列各式的值(1)x²-y²;(2)x²+4xy+3y²;(3)2x²-xy-3y²需要过程.](/uploads/image/z/2556469-37-9.jpg?t=%E5%B7%B2%E7%9F%A5x%26%23178%3B%2Bxy%3D3%2Cxy%2By%26%23178%3B%3D-2%2C%E6%B1%82%E4%B8%8B%E5%88%97%E5%90%84%E5%BC%8F%E7%9A%84%E5%80%BC%EF%BC%881%EF%BC%89x%26%23178%3B%EF%BC%8Dy%26%23178%3B%EF%BC%9B%EF%BC%882%EF%BC%89x%26%23178%3B%2B4xy%2B3y%26%23178%3B%EF%BC%9B%EF%BC%883%EF%BC%892x%26%23178%3B%EF%BC%8Dxy%EF%BC%8D3y%26%23178%3B%E9%9C%80%E8%A6%81%E8%BF%87%E7%A8%8B.)
已知x²+xy=3,xy+y²=-2,求下列各式的值(1)x²-y²;(2)x²+4xy+3y²;(3)2x²-xy-3y²需要过程.
已知x²+xy=3,xy+y²=-2,求下列各式的值(1)x²-y²;(2)x²+4xy+3y²;(3)2x²-xy-3y²需要过程.
已知x²+xy=3,xy+y²=-2,求下列各式的值(1)x²-y²;(2)x²+4xy+3y²;(3)2x²-xy-3y²需要过程.
(1)x²-y²
=(x²+xy)-(xy+y²)
=3-(-2)
=5
(2)x²+4xy+3y²
=(x²+xy)+3(xy+y²)
=3+3×(-2)
=3-6
=-3
(3)2x²-xy-3y²
=2(x²+xy)-3(xy+y²)
=2×3-3×(-3)
=6+9
=15
收起
x+y+x-y。
x²-y²=x² + xy - ( xy + y² ) = 3 + 2 = 5x²+4xy+3y² = x²+xy+3(xy+y²)=3-6=-3