已知xy是方程组①x+2y=4②x-y=-5的解,求1-x-y/x+2y÷x²-y²/x²
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已知xy是方程组①x+2y=4②x-y=-5的解,求1-x-y/x+2y÷x²-y²/x²+4xy+4y的值
![已知xy是方程组①x+2y=4②x-y=-5的解,求1-x-y/x+2y÷x²-y²/x²](/uploads/image/z/17150070-30-0.jpg?t=%E5%B7%B2%E7%9F%A5xy%E6%98%AF%E6%96%B9%E7%A8%8B%E7%BB%84%E2%91%A0x%2B2y%3D4%E2%91%A1x%EF%BC%8Dy%3D%EF%BC%8D5%E7%9A%84%E8%A7%A3%2C%E6%B1%821%EF%BC%8Dx%EF%BC%8Dy%2Fx%2B2y%C3%B7x%26%23178%3B%EF%BC%8Dy%26%23178%3B%2Fx%26%23178%3B)
①x+2y=4,②x-y=-5,
——》x=-2,y=3,
1-[(x-y)/(x+2y)]÷[(x^2-y^2)/(x^2+4xy+4y^2)]
=1-[(x-y)/(x+2y)]*[(x+2y)^2/(x-y)(x+y)]
=1-(x+2y)/(x+y)
=-y/(x+y)
=-3/(-2+3)
=-3.
——》x=-2,y=3,
1-[(x-y)/(x+2y)]÷[(x^2-y^2)/(x^2+4xy+4y^2)]
=1-[(x-y)/(x+2y)]*[(x+2y)^2/(x-y)(x+y)]
=1-(x+2y)/(x+y)
=-y/(x+y)
=-3/(-2+3)
=-3.
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