Factor
\left(r+3\right)\left(r^{2}-3r+9\right)
Evaluate
r^{3}+27
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\left(r+3\right)\left(r^{2}-3r+9\right)
Rewrite r^{3}+27 as r^{3}+3^{3}. The sum of cubes can be factored using the rule: a^{3}+b^{3}=\left(a+b\right)\left(a^{2}-ab+b^{2}\right). Polynomial r^{2}-3r+9 is not factored since it does not have any rational roots.
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