# Find Exponential Equation from data points

Hi guys I'm helping my girlfriend with her Calc 1 homework and we seem to be stuck on this one problem. Am I missing something obvious?

## Homework Equations

$P = P_0 a^t$

$\frac{5}{20} = \frac{P_0 a^1}{P_0 a^{-1}}$

$\frac{1}{4} = a^2$

$a = \frac{1}{2}$

$5 = P_0 (1/2)^1$

$P_0 = 10$

$P(t) = 10 (1/2)^t$