I have to find the general equation of a secant from any point (A,f(A)) to the point on f(x) = $\displaystyle 4^x $ where x = 2. That point is (2,16) Can someone help me develop this equation. I have an example. But they use the point (4,4) so its hard to tell what is the x and what is the y and how they are expanded and everything.