1-y-xy+x
问题描述：
1-y-xy+x
9m^2-4n^2+4n-1
(2a-b)^2+8ab
3x^2y-7xy+4y
答
1-y-xy+x=(1-y)+x(1-y)=(1-y)(1+x)9m^2-4n^2+4n-1=(3m)²-(4n²-4n+1)=(3m)²-(2n-1)²=(3m+2n-1)(3m-2n+1)(2a-b)^2+8ab=4a²-4ab+b²+8ab=4a²+4ab+b²=(2a+b)²3x^2y-7xy+4y=...