4-12x+12y+9(x-y)^2

4-12x+12y+9(x-y)^2
=4-12(x-y)+9(x-y)^2
=[3(x-y)]^2-2*[3(x-y)]*2+2^2
=[3(x-y)-2]^2
=(3x-3y-2)^2

是因式分解吗？
令x-y=t
4-12t+9t^2
=9(t^2-4/3t+4/9)
=9(t-2/3)^2
所以：9(x-y-2/3)^2

要算什么呀，我可以告诉的是这个式子可以化为

（3x-3y-2)^2

是因式分解吗？
4-12x+12y+9(x-y)^2=4-12(x-y)+9(x-y)^2=[3(x-y)-2]^2