已知x+y=1,xy=-二分之一.求x(x+y)(x-y)-[x(x+y)^2]

问题描述:

已知x+y=1,xy=-二分之一.求x(x+y)(x-y)-[x(x+y)^2]

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