Question

先化简，再求值。x的2次幂-y的2次幂/x+y-2x-2y，其中x=3，y=1/3.（要过程）

Answer 1

您好：

x的2次幂-y的2次幂/x+y-2x-2y
=（x+y）（x-y）/(x+y)-2x-2y
=x-y-2x-2y
=-x-3y
=-3-3x1/3
=-4

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Answer 2

(x²-y²)/(x+y)-2x-2y
=(x+y)(x-y)/(x+y)-2x-2y
=x-y-2x-2y
=-x-3y
=-3-3*1/3
=-4

Answer 3

原式是不是(x^2-y^2)/(x+y-2x-2y)?若是，(x^2-y^2)/（x+y-2x-2y）=(x+y)(x-y)/[(x+y)-2(x+y)]=(x-y)/(-1)=y-x，则原式=(1/3)-3=-(8/3)
如果2x-2y不属于分母，则原式=[(x+y)(x-y)/(x+y)]-2x-2y=x-y-2x-2y=-x-3y=-3-(3*1/3)=-4

Answer 4

(x²-y²)/(x+y)-2x-2y=(x+y)(x-y)/(x+y)-2x-2y=x-y-2x-2y=-x-3y=-3-3*1/3=-4