1.m^3+2m^2-9m-18 2.(x+1)(x+3)(x+5)(x+7)-9
问题描述：
1.m^3+2m^2-9m-18 2.(x+1)(x+3)(x+5)(x+7)-9
因式分解
答
1.m^3+2m^2-9m-18
=m^2(m+2)-9(m+2)
=(m+2)(m^2-3^2)
=(m+2)(m+3)(m-3)
2.(x+1)(x+3)(x+5)(x+7)-9
=[x^2+8x+7][(x^2+8x+7)+8]-9
=(x^2+8x+7)^2+8(x^2+8x+7)-9
=(x^2+8x+7+9)(x^2+8x+7-1)
=(x+4)^2(x^2+8x+6)