已知x+y=a,xy=b,求(x-y),x+y,x-xy+y的值.

问题描述:

已知x+y=a,xy=b,求(x-y),x+y,x-xy+y的值.

(x-y)=x-2xy+y=(x+y)-4xy=a-4b x+y=(x+y)-2xy=a-2b x-xy+y=(x+y)-3xy=a-3b