(x+1)(x+3)(x+5)(x+7)-9
=[(x+1)(x+7)][(x+3)(x+5)]-9
=(x^2+8x+7)(x^2+8x+15)-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)+3][(x^2+8x+7)+5]
=(x^2+8x+10)(x^2+8x+12)
=(x^2+8x+10)(x+2)(x+6)
(x+1)(x+3)(x+5)(x+7)-9怎么因式分解啊
(x+1)(x+3)(x+5)(x+7)-9
=[(x+1)(x+7)][(x+3)(x+5)]-9
=(x^2+8x+7)(x^2+8x+15)-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)+3][(x^2+8x+7)+5]
=(x^2+8x+10)(x^2+8x+12)
=(x^2+8x+10)(x+2)(x+6)