用待定系数法.
令x³+2x+m=(x-1)(x²+ax+b)
x³+2x+m=x³+(a-1)x²+(b-a)x-b
对比,得
a-1=0
b-a=2
-b=m
解得a=1 b=3 m=-3
x³+2x-3=(x-1)(x²+x+3)