(x-y)(x-2y)-(3x-2y)(x-3y),其中X=4,Y= -1,先化简,再求值

题目

(x-y)(x-2y)-(3x-2y)(x-3y),其中X=4,Y= -1,先化简,再求值
急用啊...
x^2-的^是什么呀

答案

(x-y)(x-2y)-(3x-2y)(x-3y)
=x^2-xy-2xy+2y^2-3x^2+2xy+9xy-6y^2
=-2x^2+8xy-4y^2
当X=4,Y= -1时,-2x^2+8xy-4y^2=-2*16-32-4=-68