(x-1)(x+2)(x+4)(x+7)-16
= { (x-1)(x+7)} {(x+2)(x+4)} - 16
= (x^2+6x-7)(x^2+6x+8) - 16
= (x^2+6x)^2 + (x^2+6x) - 56 - 16
= (x^2+6x)^2 + (x^2+6x) - 72
= (x^2+6x+9)(x^2+6x-8)
= (x+3)^2 (x^2+6x-8)
(x-1)(x+2)(x+4)(x+7)-16把这个式子分解因式（用10字相乘）
(x-1)(x+2)(x+4)(x+7)-16
= { (x-1)(x+7)} {(x+2)(x+4)} - 16
= (x^2+6x-7)(x^2+6x+8) - 16
= (x^2+6x)^2 + (x^2+6x) - 56 - 16
= (x^2+6x)^2 + (x^2+6x) - 72
= (x^2+6x+9)(x^2+6x-8)
= (x+3)^2 (x^2+6x-8)