Ta có:
x^5+x+1=(x^3+x^2)+x+1=x^2(x+1) + (x+1) =(x+1)(x^2+1)
\(=x^5+x+1=x^5-x^4+x^4-x^3+x^3-x^2+x^2+x+1\)
\(=x^4\left(x-1\right)+x^3\left(x-1\right)+x^2\left(x-1\right)+\left(x^2+x+1\right)\)
\(=x^2\left(x-1\right)\left(x^2+x+1\right)+\left(x^2+x+1\right)\)
\(=\left(x^2+x+1\right).\left(x^3-x^2+1\right)\)