How do you evaluate log_3 81 ? Precalculus Properties of Logarithmic Functions Functions with Base b 1 Answer Katie Lau Nov 11, 2015 The answer is 4. Explanation: log_(3)81 is the same thing as writing 3^x = 81, where you have to solve for x. 3 is the base number. 3 * 3 * 3 * 3 is 81, proving 3^4 = 81. So, 4 is the answer. Answer link Related questions What is the exponential form of log_b 35=3? What is the product rule of logarithms? What is the quotient rule of logarithms? What is the exponent rule of logarithms? What is log_b 1? What are some identity rules for logarithms? What is log_b b^x? What is the reciprocal of log_b a? What does a logarithmic function look like? How do I graph logarithmic functions on a TI-84? See all questions in Functions with Base b Impact of this question 22997 views around the world You can reuse this answer Creative Commons License