已知x(x-1)-(x^2-y)=-3,求3x^2+3y^2-6xy的值
问题描述：
已知x(x-1)-(x^2-y)=-3,求3x^2+3y^2-6xy的值
答
x(x-1)-(x^2-y)=-3
x^2-x-x^2+y=-3
-x+y=-3
x-y=3
原式=3(x^2-2xy+y^2)
=3(x-y)^2
=3×3^2
=27