Not all roles available for this page.
Sign in to view assessments and invite other educators
Sign in using your existing Kendall Hunt account. If you don’t have one, create an educator account.
For each difference, find the value of the difference by finding the value of each logarithm and then subtracting the values. Then complete the given logarithm so that it has the same value as the difference.
The first one is done for you. Discuss with your partner why it is true.
Use the pattern you noticed about differences of logarithms with the same base to write a conjecture.
If , , and , find the values of each logarithm. Explain or show your reasoning.
Let's work through some steps of a proof for your conjecture.
Start with two equations:
Rewrite both of these equations as logarithms, and circle your answers to use later.
Divide the left sides of the original equations, and set the quotient equal to the quotient of the right sides of the original equations.
Combine the exponents on the left side of the equation so that it is written with a single base.
Rewrite the last equation as a logarithm.
Use your circled equations to replace any and in that equation with equivalent logarithms.
The quotient rule for logarithms allows us to combine a difference of logarithms with the same base into a single logarithm. The quotient rule states that
For example, .
Thinking about logarithms in relation to exponents, this may make more sense. We learned in an earlier course that
By rewriting parts of that equation into their logarithm form, we can combine the pieces to prove the quotient rule.
The difference of logarithms with the same base is equivalent to a logarithm of the quotient of the arguments.