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^3-x^2)(x^2+x+1)+(x^2+x+1)
=(x^3-x^2+1)(x^2+x+1)