## Algebra 1: Common Core (15th Edition)

$C$
List the prime factors of each term. Identify the factors common to all terms. $21n^{3}=(3)\cdot 7\cdot(n\cdot n)\cdot n$ $18n^{2}=2\cdot(3)\cdot 3\cdot(n\cdot n)$ GCF= $(3)\cdot(n\cdot n)$, or $3n^{2}$. Answer: C.