Generally speaking, logarithmic function is a function with power (true number) as independent variable, exponent as dependent variable and base as constant.

Logarithmic function is one of the six basic elementary functions, in which logarithm is defined as:

If ax = N(a>；; 0, and a≠ 1), then the number x is called the logarithm of the base of n, denoted as x=logaN, and read as the logarithm of the base of n, where a is called the base of logarithm and n is called a real number.

In general, the function y = logax(a >；; 0, and a≠ 1) is called logarithmic function, that is, a function with power (real number) as independent variable, exponent as dependent variable and base constant as constant is called logarithmic function.

The bottom true logarithm is positive and the bottom true logarithm is negative. The explanation is as follows:

That is, if y=logab (where a >；; 0，a≠ 1，b & gt0)。

When 0

When a> 1, b> is at 1, y = logab & gt0.

When 0

When a> 1, 0<b< is at 1, y = logab.