Answer:
A(n) = 5 * 4^n-1
Step-by-step explanation:
How do we get the initial value? The value of A(n) when n = 1. But before that, we should find our rate of change. What is our rate of change? Well, its just 4 right!?
5, 20, 80, 320...
Notice that we just multiply 4 to a number to get the next number in the series.
So therefore, we can express the function in the following manner
A(n) = initial value * rate of change ^ n-1
