用十字相乘法做6m^2+10m+4=(6m+4)(m+1)2x^2-4x-6=2(x^2-2x-3)=2(x-3)(x+1)用分组分解法做a^2-6ab+9b^2-1=(a-3b)^2-1=(a-3b+1)(a-3b-1)y(y+2)+4x(x-y-1)=y^2+2y+4x^2-4xy-4x=y^2-4xy+4x^2-4x+2y=(2x-y)^2-2(2x-y)=(2x...