Answer:
(I will suppose that the actual equation is: N = 8*4^t instead of N = 8.4^t)
A general exponential growth can be written as:
f(x) = A*r^x
Where:
A is the initial amount.
r is the rate of growth
x is the variable.
Here we have the equation:
N = 8*4^t
Comparing this with the general form, we have:
Initial amount = 8
rate of growth = 4
variable = t
Then is easy to see that initially, there are 8 baceria present.
We also can see this if we evaluate the function in t = 0.
N(0) = 8*4^0 = 8*1 = 8
If instead, the function was:
N = 8.4^t
Then we can rewrite this as:
N = 1*(8.4)^t
And we will have:
initial amount = 1
rate of growth = 8.4
variable = t
Then in this case we have a single bacteria initially persent.