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.


Problem 7.5b: tex2html_wrap_inline135


Answer: tex2html_wrap_inline155 The exact solution is tex2html_wrap_inline137 and the approximate solution is x=-0.330482023722.


Solution:

The exponential term is already isolated.

Take the natural logarithm of both sides of the equation tex2html_wrap_inline141


eqnarray41


eqnarray46


eqnarray51



The exact answer is tex2html_wrap_inline143 and the approximate answer is tex2html_wrap_inline145


When solving the above problem, you could have used any logarithm. For example, let's solve it using the logarithm with base 37.


eqnarray58


eqnarray63


eqnarray70


eqnarray78



Check this answer in the original equation.

Check the solution tex2html_wrap_inline137 by substituting -0.330482023722 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 -0.330482023722 for x, then x=-0.330482023722 is a solution.


You can also check your answer by graphing tex2html_wrap_inline163 (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 -0.330482023722 . This means that -0.330482023722 is the real solution.


If you would like to review the answer and solution to problem 7.5c, click on problem.

If you would like to go back to the equation table of contents, click on contents.

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