该题如何因式分解:x^4-7x^3+14x^2+7x+1

题目有错?
如果把7x换成-7x有：
x^4-7x^3+14x^2-7x+1
= x^4-7x^3+12x^2 + 2x^2-7x + 1
= (x^2-3x)(x^2-4x) + x^2-3x + x^2-4x + 1
= (x^2-3x+1)*(x^2-4x+1)