\(a^5+a+1\)
\(=\left(a^5-a^2\right)+\left(a^2+a+1\right)\)
\(=a^2\left(a^3-1\right)+\left(a^2+a+1\right)\)
\(=a^2\left(a-1\right)\left(a^2+a+1\right)+\left(a^2+a+1\right)\)
\(=\left(a^2+a+1\right)\left(a^3-a^2+1\right)\)
\(a^5+a+1=a^5+a^4+a^3+a^2+a+1-a^4-a^3-a^2\)
\(=a^2\left(a^3-1\right)+\left(a^2+a+1\right)\)
\(=a^2\left(a-1\right)\left(a^2+a+1\right)+\left(a^2+a+1\right)\)
\(=\left(a^2+a+1\right)\left(a^3-a^2+1\right)\)
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