Question

先化简，再求值：[(x+y)(x-y)-(x-y)^2+2y(x-3y)]/(-4y),其中x=1，y=-2 要详细过程

谁帮我解决了问题，我就采纳谁
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Answer 1

你好：为你提供精确解答

先化简：
（x^2 - y^2 - x^2+2 xy-y^2+2xy-6 y^2)/(-4 y)
=(4xy-8y^2)/(-4y)
=-x+2y=-1-4
= -5
其他的正在为你解答。
谢谢

Answer 2

原式=(x²-y²-x²+2xy-y²+2xy-6y²)/(-4y)
=(-8y²+4xy)/(-4y)

=2y-x
=-4-2
=-6

追问

算错，
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追答

不信拉倒，再见

Answer 3

先分解（x^2-y^2-x^2+2xy-y^2+2yx-6y^2)/(-4y)
=(4xy-8y^2)/(-4y)
=-x+2y=-1-4
= -5

追问

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Answer 4

原式=(x²-y²-x²+2xy-y²+2xy-6y²)/(-4y)
=(-8y²+4xy)/(-4y)

=2y-x
=-4-1
=-5

追问

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Answer 5

x的平方-y的平方-（x的平方-2xy-y的平方）+2xy-6y的平方/4y
4xy的平方-6y的平方/4y
4*1*-2-6*-2/-8=2.5

Answer 6

是-7 =(x²-y²-x²+2xy-y²+2xy-6y²)/(-4y)
=(-8y²+4xy)/(-4y)