若x(y-1)-y(x-1)=4,求x2+y22−xy的值.

若x(y-1)-y(x-1)=4,求x2+y22−xy的值.

∵x(y-1)-y(x-1)=4,∴xy-x-xy+y=4,∴y-x=4,∴x-y=-4,∴x2+y22−xy=(x−y)22=(−4)22=8.