To begin a bacteria study, a petri dish had 2800 bacteria cells. Each hour since, the number of cells has increased by 7.2%. Let t be the number of hours since the start of the study. Let y be the number of bacteria cells. Write an exponential function showing the relationship between y and t.​

The function that models exponential growth is:

P(t) = P0*(1 + r)^t, where

P0 = P(0) is the initial value of P

r is the growth rate as a decimal

In our case we have:

P(0) = 2800

r = 0.035 or 3.5%

P(t) = 2800*(1 + 0.035)^t

P(t) = 2800*(1.035)^t

The same exponential function written using y and t is:

y = 2800*1.035^t.

Explanation: https://softmath.com/algebra-word-problems/to-begin-a-bacteria-study-a-petri-dish-had-2800-bacteria