Exponential Growth and Decay Exponential Functions An exponential function with base b is defined by f (x) = abx where a ≠0, b > 0 , b ≠1, and x is any real number. The base, b, is constant and the exponent, x, is a variable.Notice: The variable x is an exponent. As such, the graphs of these functions are not straight lines. In a straight line, the "rate of change" … [Read more...] about Exponential Growth and Decay