Exponential from Two Points-Sections 5.1, 2, 4
Given two points, find C and a for exponential equation.
For video explanation, see
https://www.khanacademy.org/math/trigonometry/exponential_and_logarithmic_func/exp_growth_decay/v/constructing-linear-and-exponential-functions-from-graph
or
http://patrickjmt.com/finding-the-equation-of-an-exponential-function/