Can someone be nice enough to help me please ?

Question

anonymous · Answer

Whats the question?

wintersuntime · Answer

http://westada.org/cms/lib8/ID01904074/Centricity/Domain/793/3.7%20What%20Comes%20Next.Later.pdf

wintersuntime · Answer

I need help with function A and B

wintersuntime · Answer

@peachpi

anonymous · Answer

look at the y's to figure out the pattern. What are they doing to get to the next number? Think in terms of addition and multiplication

wintersuntime · Answer

multiplying by 2

anonymous · Answer

right, so that's the answer to #1

wintersuntime · Answer

For number 2 what it be f(x) = f(n-1) x 2

anonymous · Answer

For the recursive formula, the first thing is to write the first term. It looks like they're using function notations, so start with f(1). y is 5 when x is 1, so the first part is
$$f(1)=5$$
Then since it's multiplying by 2,
$$f(n)=2f(n-1)$$

anonymous · Answer

make sense?

wintersuntime · Answer

So it would only be f(n)= 2f(n-1)

anonymous · Answer

no, you need to keep f(1) = 5 as well.
The recursive formula only gives you a term if you know the previous term

wintersuntime · Answer

so f(1)=5 2f(n-1)

anonymous · Answer

yes

anonymous · Answer

actually, no

wintersuntime · Answer

between 5 and 2 i don't put nothing ?

anonymous · Answer

Write it like this
$$f(1)=5, f(n)=2f(n-1)$$

wintersuntime · Answer

oh it was like that

anonymous · Answer

It's saying that the first term is 5.
Then to find the second term, multiply the first one by 2.
Then to find the third term, multiply the second by 2.
and so on.
So with a recursive formula, if you want to know the 67th term, you have to know the 66th. But to know the 66th, you have to know the 65th and so on. It's only useful to point out the pattern. Not really useful for anything else

anonymous · Answer

The explicit one is the useful one.
$$f(n)=ar^{n-1}$$
a = first term
r = number you multiply by (called the common ratio)
Plug in your numbers to that formula to get the explicit formula

wintersuntime · Answer

so i plug in 65?

anonymous · Answer

no, your first term is 5, and you're multiplying by 2.
So plug in 5 for a and 2 for r to get the formula

anonymous · Answer

$$f(n)=5(2)^{n-1}$$

wintersuntime · Answer

oh

anonymous · Answer

the function for A is geometric because it's multiplying by the same number to get to the next term.

wintersuntime · Answer

Isn't it geometric

anonymous · Answer

yeah geometric

anonymous · Answer

I gtg. sorry I can't stay to help on the next one

wintersuntime · Answer

its okay