[(x-2y)平方+(x-2y)(x+2y)-2x(2x-y)]除以(-2x) 其中x=2分之1，y=3 这题怎么算？

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[(x-2y)²+(x-2y)(x+2y)-2x(2x-y)]÷(-2x)
=[(x-2y)（冲闭森x-2y+x+2y)-2x(2x-y)]÷(-2x)
=2x（散亩态启x-2y-2x+y)÷(-2x)
=-(-x-y)
=x+y
=½+3
=3.5

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