[2x-（x+y)(x-y)][(2-x)(x+2)+(-y-2)(2-y)],其中x=-1/2,y=-1

[2x-（x+y)(x-y)][(2-x)(x+2)+(-y-2)(2-y)]
=(-1+3/2*1/2)(5/2*3/2-1*3)
=-1/4*3/4
=-3/16 或

[2x-（x+y)(x-y)][(2-x)(x+2)+(-y-2)(2-y)]
=(2x-x~+y~)(4-x~-4+y~)
=(2x-x~+y~)(y~-x~)
把x=-1/2,y=-1代入
＝（-1-1/4+1）（1-1/4）
＝－3/16

～为平方

[2x-（x+y)(x-y)][(2-x)(x+2)+(-y-2)(2-y)]
=[2x-x^+y^][4-x^-4+y^]
=[2x-x^+y^][-x^+y^]
=-2x~+x!-y^x^+2xy^-x^y^+y!
=-2x~+x!-2y^x^+2xy^+y!
把x=-1/2,y=-1带入上式：
=1/4+1/16+1+1+1
=53/16
（其中^为平方 ~为3次方 !为4次方）

解：原式={2X-X*X+Y*Y}{4-X*X+{（-Y）*（-Y）-4}
={2X-X*X+Y*Y}{Y*Y-X*X}
然后带入就行了

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