(1)x³-9x+8
=x³-1-9x+9
=（x-1)（x²+x+1)-9（x-1）
=（x-1)(x²+x+1-9)
=(x-1)(x²+x-8)
(2)(x²-1)(x+3)(x+5)+12
=(x+1)(x+3)(x-1)(x+5)+12
=(x²+4x+3)(x²+4x-5)+12
=(x²+4x)²-2(x²+4x)-15+12
=(x²+4x)²-2(x²+4x)-3
=(x²+4x-3)(x²+4x+1)
(3)x²+xy-6y²
=(x+3y)(x-2y)
抄的 选我哦哦