Let's factor in $ℝ$: $c^3+c$

This expression can be factorized into: $c·(c^2+1)$

ⓘ Factor out the common factor $c$■A square being never negative, $c^2+1$ is never zero and cannot be factored in ℝ

▶Factored expression:   $c·(c^2+1)$