3m+mn+21+7n
Group the first two terms and the last two terms.
(3m+mn)+21+7n
Factor out the greatest common factor (GCF) from each group.
m⋅(3+n)+7(3+n)
m⋅(3+n)+7(3+n)
Factor the polynomial by factoring out the greatest common factor, 3+n.
(3+n)(m+7)
Factor by Grouping 3m+mn+21+7n
