Answer:
f(4) = 256
Explanation:
f(1) = 4
f(n) = 4f(n-1)
f(2) = 4 f(1) = 4 x 4 = 16
f(3) = 4 f(2) = 4 x 16 = 64
f(4) = 4 f(3) = 4 x 64 = 256
The general formula is f(n) = 4ⁿ
This is a geometric progression with first term 4 and common ratio 4 so it is usual to write this as
f(n) = a₁ · 4ⁿ⁻¹
with a₁ the first term = 4
So f(n) = 4 x 4ⁿ⁻¹
(which is the same as 4ⁿ