已知x+y=1,xy=-二分之一,求x（x+y)(x-y)-x(x+y)²_其他解答

已知x+y=1,xy=-二分之一,求x（x+y)(x-y)-x(x+y)²

人气：112 ℃　时间：2019-08-19 09:14:29

解答

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