Concept:
Logarithms are an alternate way to think about exponents: if y = bx, then x = logb(y). The base b of the exponential form is also called the base in the exponential form, and is subject to the same restriction as the base of an exponent: it must be a positive number. Furthermore, y must be positive.
To make a function out of a logarithm, let f(x) = a + nlogb(x - c), with n ≠ 0 and b ≠ 1. The extra parameters allow for transformations of the graph of the basic logarithm function f(x) = logb(x).
