1. 6.3A – Logarithms and Logarithmic Functions Objective: TSW evaluate logarithmic expressions.

2. Definition of a Logarithmic Function For x > 0 and b > 0, y = log b x is equivalent to b y = x. So, a logarithm allows us to solve for unknown exponents since a logarithm is an exponential equation Logarithmic form: y = log b x Exponential Form: b y = x.

3. Examples…. 1. Write each equation in its equivalent exponential form. a. 2 = log 5 xb. 3 = log b 64c. log 3 7 = y We will use the fact that: y = log b x means b y = x,

4. Examples… 2.Write each equation in it’s equivalent logarithmic form. a. 2 r = 10b. 17= b 3.2 c. 12 2 = 144

5. Now Let’s Apply the Definition to Solve. Here are the steps: 1.Set the logarithm equal to y 2.Rewrite the logarithm in exponential form 3.Break the bases down so they are the same!!! 4.REMEMBER, if the bases are equal, the exponents MUST BE equal! 5.Set the exponents equal and solve for y. 6.CHECK YOUR SOLUTION! Logarithmic form: y = log b x Exponential Form: b y = x.

6. Let’s Try a Few… 3. Evaluate a. log 2 16b. log 3 9

7. 4.Evaluate a. log 5 (1/25) b. log 25 5

8. Homework! Pg. 496 #’s 1-7(all), 13-23(odds), 25-36(all).