x(x+y)(x-y)-x(x+y)^2
=x(x+y)(x-y-x-y)
=-2xy(x+y) x+y=1,xy=-1/2
=-2*(-1/2)*1
=1
x(x+y)(x-y)-x(x+y)^2
=x(x+y)[(x-y)-(x+y)]
=x(x+y)(x-y-x-y)
=-2xy(x+y)
=-2×(-1/2)×1
=1
x(x+y)(x-y)-x(x+y)^2
=x(x+y)[(x-y)-(x+y)]
=x(x+y)(x-y-x-y)
=-2xy(x+y)
=-2*(-1/2)*1
=1
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