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Pre-Calculus · Axiom Academy
The Question Logarithms Answer A logarithm isn't a new number to memorize — it's a question. "To what power?" You already know how to multiply. The hard question runs the other way. Going forward is easy: 2 times itself three times is 8. But suppose someone hands you the 8 and the 2, and asks the reverse — "2 raised to what power gives 8?" That missing exponent is the whole point of a logarithm. Watch the powers of 2 climb, then you'll hunt the exponent yourself. Watch the exponent tick up from 0 to 3. Each step doubles the value — 1, 2, 4, 8 — and the marker climbs the curve y = 2ˣ. The exponent that lands the marker on 8 is the answer to "2 to what power equals 8?" The exponent 3 is what we'll soon write as log₂ 8 — the power of 2 that produces 8. Search for the exponent that lands on 8 Slide the exponent up and down. The marker rides the curve y = 2ˣ and the value 2^exp updates live. Find the exponent that makes 2^exp land exactly on the target line at 8 — that exponent is what a logarithm reports. When 2^exp reads 8, the exponent reads 3. That is exactly log₂ 8 = 3. A logarithm is exponentiation run backwards Drag the point along the exponential curve y = 2ˣ. Its mirror image — reflected across the dashed line y = x — rides the logarithm curve y = log₂ x. Exp turns an exponent into a value; log turns that value back into the exponent. They undo each other. Read the pair both ways: 2ᵉ = x going forward, and log₂ x = e coming back. Same fact, two directions.
This is the written version of the interactive lesson above. See the full Pre-Calculus course.