分组分解法.
问题描述：
分组分解法.
1.x^2+3y-xy-3x
2.(y+2)x^2+(y+2)x-12y-24
3.m^2x^2+n^2y^2-m^2y^2-n^2x^2
4.x^2-4y^2-x-2y
答
1)X²+3Y-XY-3X=X²-XY-(3X-3Y)=X(X-Y)-3(X-Y)=(X-Y)(X-3）2）（Y+2)X²+(Y+2)X-12Y-24=(Y+2)X²+(Y+2)X-12(Y+2)=(Y+2)(X²+X-12)=(Y+2)(X-3)(X+4)3)m²X²+n²Y²-m²Y&su...