2x^4-x^3+3x^2-1
=2x^4+x^3-2x³-x²+4x^2-1
=x³(2x+1)-x²(2x+1)+(2x+1)(2x-1)
=(2x+1)(x³-x³+2x-1)
即另一个因式为x³-x²+2x-1.