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# find the nth term watch

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1. 2/3 , 6/7 , 14/15 , 30/31

i split it from top and bottom:
2, 6, 14, 30...
3, 7, 15, 31...

I can't seem to do much with this, im guessing its 4^n then somthing,
as the 'common' difference is 4, (i use ' ' seeing as its not really common, im sure you know what i mean), but i cant really see what to do now, is there some method/formula to work something like this out?
2. Well, looking at the bottom first, an obvious pattern jumps out (related to 4^n)
3. Not sure 4^n is really the thing to be looking at...
4. Spoiler:
Show
Top:
Bottom:

I know it's not really the nth term, but it's a start. :P
5. It looks like n+(n+1)+1/n+(n+1)+2

ie, 2+3+1 = 6
2+3+2 = 7

6+7+1 = 14
6+7+2 = 15 etc etc
6. Think I got it.

Spoiler:
Show
7. (Original post by Pork and Beans)
Spoiler:
Show
Top:
Bottom:

I know it's not really the nth term, but it's a start. :P
yh, i saw that, but i dont know how you'd work out an nth term formula from that
8. (Original post by Pork and Beans)
Think I got it.

Spoiler:
Show
that does seem to work, how did u get that? how come its 2^ , rather than 4^
9. ok yep thanks i get it now, your adding 2^n+1 every time, thanks
10. The difference in terms is being multiplied by 2 with each successive term, this is your clue that you need to be thinking in powers of two.

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