Answer:
4
Step-by-step explanation:
we have
[tex]f(x)=2(4^x)[/tex]
This is a exponential growth function of the form
[tex]f(x)=a(1+r)^x[/tex]
where
a is the initial value
(1+r) is the base of the exponential function or multiplicative rate of change of the function
r is the rate of change
In this problem we have
[tex]a=2\\(1+r)=4\\r=4-1=3=300\%[/tex]
therefore
4 is the base of the exponential function or multiplicative rate of change of the function
