(x+y-z)²+(x+y-z)(x+y+z)-2z(x-y)
=[(x+y)-z]²+[(x+y)-z][(x+y)+z]-2z(x-y)
=(x+y)²-2z(x+y)+z²+(x+y)²-z²-2z(x-y)
=-2z[(x+y)+(x-y)]
=-2z(2x)
=-4xz

應(yīng)該是式子錯(cuò)了!沒(méi)有答案!


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