=x^5+x-1
=x^5+x^2-x^2+x-1
=x^2(x^3+1)-(x^2-x+1)
=x^2*(x+1)(x^2-x+1)-(x^2+x+1)
=(x^2-x+1)[x^2(x+1)-1]
=(x^2-x+1)(x^3+x^2-1)