Final answer:
The exponential equation to model the decay of melatonin after t time periods is A(t) = 10 · (1/2)t/30.
Step-by-step explanation:
To model the exponential decay of melatonin after time t periods, we can use the formula A(t) = A0 · (1/2)t/r, where A(t) is the amount of melatonin after t periods, A0 is the initial amount of melatonin (10 milligrams in this case), and r is the half-life of melatonin (30 minutes). So the exponential equation to model this is A(t) = 10 · (1/2)t/30.