An exponential function is denoted by f(x)=abx, where a=0, b>0 and b=1. Answer the following questions related to this general form.
a. (i) Define an exponential function and state its domain and range.
b. (ii) Prove that the y-intercept of the graph of an exponential function f(x)=abx is (0,a).
c. (iii) Let an exponential function pass through its y-intercept (0,a) and an additional point (x1,y1) with x1=0. Show algebraically that b=(ay1)1/x1.