解
x³-3x-2
=x³-x-2x-2
=x(x²-1)-2(x+1)
=x(x-1)(x+1)-2(x+1)
=(x+1)[x(x-1)-2]
=(x+1)(x²-x-2)
=(x+1)(x-2)(x+1)
=(x+1)²(x-2)