A sequence is defined by the recursive formula f (n + 1) = f(n) – 2. If f(1) = 18, what is f(5)?

Question

anonymous · Answer

Start off by plugging in 1 into recursion. What would that give you?

anonymous · Answer

i would say 80

anonymous · Answer

Well, if you plug in n = 1, youd have this:
$f(1+1) = f(1) - 2$

That's what I meant to do

anonymous · Answer

So just to finish off the idea:

$f(1+1) = f(1) - 2$

$f(2) = f(1) - 2$  But f(1) is 18 as the problem told us, so

$f(2) = 18 -2$

$f(2) = 16$

That make sense what I did?

anonymous · Answer

omg thank you

anonymous · Answer

i hate math tbh

anonymous · Answer

Most people do, lol. 

But yeah, the next thing youd do is plug in 2:

$f(2+1) = f(2) - 2$

$f(3) = f(2) - 2$

$f(3) = 16-2$

$f(3) = 14$

So the idea is Im going to keep doing this until I get to f(5). Or you might be able to see the pattern and predict what f(5) would be from here. Either way, think you got it from here?