X^5+x+1=
=x^5+x^4-x^4+x^3-x^3-x^2+x^2+x+1=
=x^3* (x^2+x+1)-x^2* (x^2+x+1)+x^2+x+1=
=(x^2+x+1)(x^3-x^2+1)
Baftă!