Math basics › Exponents and logs
Exponential growth and decay
The shape
y = a·bˣ. b > 1 grows, 0 < b < 1 decays. a is the starting amount, at x = 0.
It is a rate, not a step
Exponential means multiplying by the same factor each period, which is why it starts slow and then goes vertical.
Doubling and halving
Solve bˣ = 2 with logs to find a doubling time; bˣ = ½ for a half-life.