(x-y)^2-5x+5y
=(x-y)^2-5(x-y)
将x-y=2带入原式
原式=2^2-5X2
=4-10
=-6
(2x^2+3ax-y)-2(bx^2-3x+2y-1)
2x^2+3ax-y-2bx^2+6x-4y+2
=(2-2b)x^2+(3a+6)x-5y+2
好了,a和b不知道,也不好再进行了这个题.