Logarithms: The Basics and Essential Rules
Logarithms are the inverse of exponentials - if a^x = n, then log_a n = x. Think of it as asking "what power do I need to raise 'a' to get 'n'?" When you see a log with no base written, it's base 10, and 'ln' means log base e (natural logarithm).
There are several fundamental logarithm rules you absolutely need to memorise. Log_a(1) always equals 0, log_a(a) always equals 1, and log_a(0) is undefined. These make sense when you think about what powers give you these results.
The operational rules are where logarithms become really powerful. When multiplying inside a log, you can split it into addition: log_a(xy) = log_a(x) + log_a(y). Division becomes subtraction: log_ax/y = log_a(x) - log_a(y). Powers can be brought out front: log_axn = nยทlog_a(x).
Quick Tip: All these logarithm rules come directly from the laws of indices - they're just the flip side of exponential rules you already know!
The change of base formula log_a n = logbโn/logbโa lets you convert between different bases, which is essential when using calculators that only have log and ln buttons.