If you would like an in-depth review of logarithms, the rules of logarithms, logarithmic functions and logarithmic equations, click on logarithmic function.
Solve for x in the following equation.
The equation is valid only if x2-18x+80>0 or
Isolate the log term..
The exact answers are and the approximate answers are 16.071068 and 1.928932.
These answers may or may not be the solutions. You must check them with the original equation, either by a numerical substitution or by graphing.
Check the answer by substituting 16.071068 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.
Check the answer by substituting 1.928932 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.
Graph the function
If you would like to test yourself by working some problems similar to this example, click on problem.
If you would like to go back to the previous section, click on previous.
If you would like to go back to the equation table of contents, click on contents.
This site was built to accommodate the needs of students. The topics and problems are what students ask for. We ask students to help in the editing so that future viewers will access a cleaner site. If you feel that some of the material in this section is ambiguous or needs more clarification, or you find a mistake, please let us know by e-mail.
S.O.S. MATHematics home page
Do you need more help? Please post your question on our S.O.S. Mathematics CyberBoard.