# How do you use the Change of Base Formula and a calculator to evaluate the logarithm #log 4^20#?

##### 1 Answer

Aug 15, 2015

#### Explanation:

There is a good possibility that the intended question is to find

In any case the change of base formula says (in its general form) that

For a, b, x positive,

#log_b x = log_a x/(log_a b)#

Because calculators tend to have built-in functions for base 10 logs,

For b, x positive,

#log_b x = log x/(log b)" "# or#" "log_b x = ln x/(ln b)#

The sequence of button to press depends on the calculator you are using.

On the calculator that is included in windows (scientific view)

press: 20 "ln" / 4 "ln" =