(1)分解因式；3m(2x-y)^2-3mn^2 (2)已知x(x-1)-(x^2-y)=-2,求2分之x^2+y^2-xy的值
问题描述：
(1)分解因式；3m(2x-y)^2-3mn^2 (2)已知x(x-1)-(x^2-y)=-2,求2分之x^2+y^2-xy的值
答
3m(2x-y)²-3mn²
=3m[(2x-y)²-n²]
=3m(2x-y+n)(2x-y-n)
x(x-1)-(x²-y)=-2
x²-x-x²+y=-2
y-x=-2
x-y=2
(x²+y²)/2-xy
=(x²-2xy+y²+2xy)/2-xy
=(x-y)²/2+xy-xy
=(x-y)²
=2²
=4