We can factor by grouping like so
3v^2 + 16v + 5
3v^2 + 15v + v + 5
3v(v + 5) + 1(v + 5)
(3v+1)(v+5)
---------
Check:
(3v+1)(v+5)
w(v+5) ... let w = 3v+1
vw + 5w
v(w) + 5(w)
v(3v+1) + 5(3v+1) .... plug in w = 3v+1
3v^2+v + 15v + 5
3v^2 + 16v + 5
We get the original expression again, which confirms the answer.