#7 What is f(4) if f(1) = 3.2 and f(x + 1) = 2.5f(x)?

Explanation:

We're given f(1) = 3.2 which says the first term of the sequence is 3.2

To find the second term, we use the other equation, which is the recursive equation. Plug in x = 1 to get...

f(x+1) = 2.5*f(x)

f(1+1) = 2.5*f(1)

f(2) = 2.5*f(1)

f(2) = 2.5*3.2

f(2) = 8

The second term is 8. We multiplied the previous term (3.2) by the factor 2.5 to get this second term.

The third term is handled pretty much in a similar fashion

third term = 2.5*(second term)

third term = 2.5*8

third term = 20

Lastly, the fourth term f(4) is...

f(x+1) = 2.5*f(x)

f(3+1) = 2.5*f(3)

f(4) = 2.5*f(3)

f(4) = 2.5*20

f(4) = 50

The fourth term is 50.

The first four terms are: 3.2, 8, 20, 50