[tex]Method\ \#1:\\\\\text{Factors of 28:}\ 1,\ 28,\ 2,\ \boxed{14},\ 4,\ 7\\\\\text{Factors of 42:}\ 1,\ 42,\ 3,\ \boxed{14},\ 6,\ 7\\\\GCF(28,\ 42)=\boxed{14}\\---------------------------\\Method\ \#2:\\\\\begin{array}{c|c}28&2\\14&2\\7&7\\1\end{array}\qquad28=\boxed{2}\cdot2\cdot\boxed{7}\\\\\begin{array}{c|c}42&2\\21&3\\7&7\\1\end{array}\qquad42=\boxed2\cdot3\cdot\boxed7\\\\GCF(28,\ 42)=\boxed2\cdot\boxed7=14[/tex]
