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. under Algebra.

Solve for x in the following equation.

Example 3:tex2html_wrap_inline155 tex2html_wrap_inline240

Isolate the exponential term.

Divide both sides of the equation by 8


eqnarray29


eqnarray33


eqnarray39



Take the natural logarithm of both sides of the equation tex2html_wrap_inline244


eqnarray45


eqnarray48


eqnarray52


eqnarray54


eqnarray58


eqnarray61


eqnarray65


eqnarray69


eqnarray73


eqnarray77



The exact answers are tex2html_wrap_inline254 and the approximate answers are -0.664200382745 and -6.33579961726.



Your exact answer may differ dependent how what logarithm you used to solve the problem. However, all forms of the correct answer will simplify to the same approximate answer.


When solving the above problem, you could have used any logarithm. For example, let's solve it using the logarithmic with base 29.


eqnarray29


eqnarray87


eqnarray93


eqnarray101


eqnarray108


eqnarray115


eqnarray122


eqnarray130


eqnarray61


eqnarray65


eqnarray69


eqnarray73


eqnarray149



The exact answers are tex2html_wrap_inline254 and the approximate answers are -0.664200382745 and -6.33579961726.



Check these answers in the original equation.



Check the solution tex2html_wrap_inline262 by substituting -0.664200382745 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 -0.664200382745 for x, then x=-0.664200382745 is a solution.


Check the solution tex2html_wrap_inline274 by substituting -6.33579961726 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 -6.33579961726 for x, then x=-6.33579961726 is a solution.


You can also check your answer by graphing tex2html_wrap_inline286 (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 -6.33579961726 and -0.664200382745.. This means that -6.33579961726 and -0.664200382745 are the real solutions.








If you would like to work another example, click on Example


If you would like to test yourself by working some problems similar to this example, click on Problem


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