a) Ta có: \(x^{10}+x^5+1\)
\(=x^{10}-x+x^5-x^2+x^2+x+1\)
\(=x\left(x^9-1\right)+x^2\left(x^3-1\right)+\left(x^2+x+1\right)\)
\(=x\left(x^3-1\right)+x^2\left(x^3-1\right)+\left(x^2+x+1\right)\)
\(=\left(x^3-1\right)\left(x+x^2\right)+\left(x^2+x+1\right)\)
\(=\left(x^2+x+1\right)\left(x-1\right)\left(x+x^2\right)+\left(x^2+x+1\right)\)
\(=\left(x^2+x+1\right)\left(1+x^2+x^3-x-x^2\right)\)
\(=\left(x^2+x+1\right)\left(x^3-x+1\right)\)