You can use synthetic division to find the other factor, or you can simply divide the leading and trailing terms by the numbers you have. (This works if the binomial you have is truly a factor of the trinomial, which it is.)
2g²/2g = g
140/14 = 10
Your other factor (the length) is g+10.
(2g² +34g +140) = (2g +14)*(g +10)
