Three consecutive positive odd integers a, b and c satisfy b^2 - a^2 = 72 and c^2 - b^2 > 0. What is the value of c^2 - b^2?
b^2 - a^2 =72
(b - a) ( b + a) = 72
(19 -17) (19 + 17) = 72
(2) ( 36) = 72
a = 17 b =19 c =21
c^2 - b^2 = 21^2 - 19^2 = (21 - 19) (21 + 19) = (2) (40) = 80
