1.x^3-1=(x-1)(x^2+x+1)
=(x-1){(x+1/2)^2+3/4}
=(x-1)(x+1/2+√3/2i)(x+1/2-√3/2i)
2.x^3-8=(x-2)(x^2+2x+4)
=(x-2){(x+1)^2+3}
=(x-2)(x+1+√3i)(x+1-√3i)
3.x^4-1=(x^2+1)(x^2-1)
=(x+i)(x-i)(x+1)(x-1)
4.x^4+1=(x^2+i)(x^2-i)
=(x+√i*i)(x-√i*i)
而√i=±(√2/2+√2/2i),具体求解过程参加参见
http://zhidao.baidu.com/question/30146553.html,这里取正
所以=(x+√2i/2-√2/2)(x-√2i/2+√2/2i)