SOLVING EXPONENTIAL EQUATIONS




Note:

If you would like an in-depth review of exponents, the rules of exponents, exponential functions and exponential equations, click on exponential function.

Solve for x in the following equation.

Example 2: tex2html_wrap_inline124

The exponential term is already isolated.

Take the natural logarithm of both sides of the equation tex2html_wrap_inline126


eqnarray27


eqnarray30


eqnarray33



The exact answer is tex2html_wrap_inline128 and the approximate answer is tex2html_wrap_inline130

When solving the above problem, you could have used any logarithm. For example, let's solve it using the logarithm with base 8.


eqnarray40


eqnarray43


eqnarray50


eqnarray58



Check this answer in the original equation.


Check the solution tex2html_wrap_inline136 by substituting 1.9534452978 in the original equation for x. If the left side of the equation equals the right side of the equation after the substitution, you have found the correct answer.

Since the left side of the original equation is equal to the right side of the original equation after we substitute the value 1.9534452978 for x, then x=1.9534452978 is a solution.



You can also check your answer by graphing tex2html_wrap_inline148 (formed by subtracting the right side of the original equation from the left side). Look to see where the graph crosses the x-axis; that will be the real solution. Note that the graph crosses the x-axis at 1.9534452978. This means that 1.9534452978 is the real solution.


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