ACT Preparation / Unit 12 ACT 1110 short lesson, about 20 seconds
What a Logarithm Is
Captions available
The idea
The logarithm log_b(x) is the exponent b must be raised to in order to give x: log_b(x) = y means bʸ = x.
In practice
log₂ 8 = 3, because 2³ = 8; log₅ 1 = 0, because 5⁰ = 1.
Where people slip
A logarithm is an exponent. Its input must be positive, since bʸ is never zero or negative.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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