Answer:
I think a possible equation can be; f(n) = 4(2)ⁿ
f(n) = a * bˣ
Where;
f(n) = the function of f for every n value
a = Initial value (in this case it would be 4)
b = Rate of change (in this case it would be 2, since the bacteria doubles)
x = exponent (in this case it would be n)
So our final equation would be:
f(n) = 4(2)ⁿ
Hope this helps!