已知x(x-1)-(x2-y)=-3,则x2+y2-2xy的值为?
问题描述:
已知x(x-1)-(x2-y)=-3,则x2+y2-2xy的值为?
答
∵x(x-1)-(x2-y)=-3,
∴x2-x-x2+y=-3,
∴x-y=3,
而x2+y2-2xy=(x-y)2,
∴x2+y2-2xy=9.