Logarithms

Undoing exponentials

An interactive lesson with 9 steps, about 8 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• $\log_b y$ is the power $b$ must be raised to in order to get $y$.
• $\log(xy) = \log x + \log y$: multiplication turns into addition.
• $y = b^x$ and $y = \log_b x$ are inverses, mirror images in the line $y = x$.

Steps

1. Powers of two
2. What a logarithm is
3. Compute
4. The log of 1
5. Multiplying becomes adding
6. Use the rule
7. Mirror images
8. When?
9. Earthquakes