Answer:
exponential growth
Step-by-step explanation:
The function type is identified by where the variables are, and what their exponents are.
When the variable is in the exponent of an expression, the function is called an exponential function.
When the base of an exponential function has a magnitude greater than 1, the function is a growth function. When it is less than 1, the function is a decay function.
Here, the base is 4, which is greater than 1.
The function is an exponential growth function.
