Algebra 2 · Unit 7 · Topic 7.2
Product, Quotient, and Power Rules
For positive M and N and a valid base b, log_b(MN) = log_b(M) + log_b(N), log_b(M/N) = log_b(M) − log_b(N), and log_b(Mʳ) = r log_b(M).
Definition and explanation
For positive M and N and a valid base b, log_b(MN) = log_b(M) + log_b(N), log_b(M/N) = log_b(M) − log_b(N), and log_b(Mʳ) = r log_b(M). Domain assumptions are part of these identities.
Worked example
For x > 0, expand ln(5x³) as ln(5) + 3ln(x). If x = e, the expression becomes ln(5) + 3, matching ln(5e³).
Common mistake
There is no corresponding rule ln(M + N) = ln(M) + ln(N); multiplication and addition are different operations.
Key takeaway
For positive M and N and a valid base b, log_b(MN) = log_b(M) + log_b(N), log_b(M/N) = log_b(M) − log_b(N), and log_b(Mʳ) = r log_b(M).
Explain each step of the worked example, then check the units, signs, and conditions that apply.
Further reading
Topic coverage was checked against the openly available OpenStax Intermediate Algebra 2e, Algebra and Trigonometry 2e, and Introductory Statistics 2e textbooks. The explanations and examples on this site are independently written; textbook prose, exercises, and artwork are not reproduced.