求25(x-2 y)^2-4(3x+y)^2的值
问题描述：
求25(x-2 y)^2-4(3x+y)^2的值
是因式分解
答
25(x-2 y)^2-4(3x+y)^2=[5(x-2 y)]²-[2(3x+y)]²=[5(x-2 y)+2(3x+y)][5(x-2 y)-2(3x+y)]=(5x-10y+6x+2y)(5x-10y-6x-2y)=(11x-8y)(-x-12y)=-(11x-8y)(x+12y)=(8y-11x)(12y+x)