x³+x²-3x+1
当x=1时；方程x³+x²-3x+1=0
所以x³+x²-3x+1的一个因式为(x-1)
x³+x²-3x+1
=x³+x²-2x-x+1
=x(x+2)(x-1)-(x-1)
=(x-1)(x²+2x-1)