x5 +x4 +1 = x5 +x4 +1 +x3 +x2 +x -(x3 +x2 +x) = (x5 +x4 +x3) +(x2 +x +1) -(x3 +x2 +x) = x3(x2 +x+1) +(x2 +x +1) -x(x2 +x +1)
= (x2 +x +1)(x3 -x +1)
. \(x^5+x^4+1=x^5-x^2+x^4-x+x^2+x+1\) \(=x^2\left(x^3-1\right)+x\left(x^3-1\right)+x^2+x+1\)
\(=x^2\left(x-1\right)\left(x^2+x+1\right)+x\left(x-1\right)\left(x^2+x+1\right)+\left(x^2+x+1\right)\)\(=\left(x^2+x+1\right)\left(x^4+2x^3+2x^2+x+1\right)\)