Answer:
the growth factor is 4
Explanation:
We are given f(x) is exponential function
so,

where
a is the initial value
b is output value increase as each input value increases by 1
so, we have to find 'b'
we can select any two points and then find 'b'
At x=1 , f(x)=4:
we can plug these values

At x=3 , f(x)=64:
we can plug these values

now, we can divide both equations
and we get

we can simplify it


So, the growth factor is 4