Factor
\left(r-2\right)\left(r^{2}+2r+4\right)
Evaluate
r^{3}-8
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\left(r-2\right)\left(r^{2}+2r+4\right)
Rewrite r^{3}-8 as r^{3}-2^{3}. The difference 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}+2r+4 is not factored since it does not have any rational roots.
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