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# [5 ^ k] - [5 ^ (k-1)]

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Senior Manager
Joined: 05 Oct 2008
Posts: 258
[5 ^ k] - [5 ^ (k-1)] [#permalink]

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Updated on: 17 Nov 2008, 02:52
How do you solve for this?

[5 ^ k] - [5 ^ (k-1)]

Do not have the AC - only have the OA, will post it later.

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Originally posted by study on 16 Nov 2008, 09:19.
Last edited by study on 17 Nov 2008, 02:52, edited 1 time in total.
Current Student
Joined: 28 Dec 2004
Posts: 3288
Location: New York City
Schools: Wharton'11 HBS'12

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16 Nov 2008, 10:08
study wrote:
How do you solve for this?

5^k - 5 ^k-1

Do not have the AC - only have the OA, will post it later.

5^(k-1)(5-1) =4*5^(k-1)
Director
Joined: 14 Aug 2007
Posts: 695

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17 Nov 2008, 00:56
study wrote:
How do you solve for this?

5^k - 5 ^k-1

Do not have the AC - only have the OA, will post it later.

Study,

Can you please put brackets when you post such questions?
Though this problem is pretty straightforward, putting the brackets makes it much easier for folks to understand the problem.
Senior Manager
Joined: 05 Oct 2008
Posts: 258

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Updated on: 17 Nov 2008, 04:13
Agreed.

Thanks for your suggestion. have edited the qs accordingly

Originally posted by study on 17 Nov 2008, 02:28.
Last edited by study on 17 Nov 2008, 04:13, edited 1 time in total.
Director
Joined: 14 Aug 2007
Posts: 695

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17 Nov 2008, 02:37
study wrote:
I post questions exactly the way they are presented. I prefer not to alter the original qs, which could possibly alter its interpretation.

I am not asking you to alter original Q.
What I wanted to say is that, when you see, say 2^(3+x) on gmat
it is clear to you that it is $$2^(3+x)$$, but when you post on forum it may look like (2^3)+ x. If you avoid such a confusion it wont make the question ambiguous.
Current Student
Joined: 28 Dec 2004
Posts: 3288
Location: New York City
Schools: Wharton'11 HBS'12

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17 Nov 2008, 09:17
1
you neeed to factor the power so that you can manipulate easily..

say you have 5^x and 5^x-1 then if you factor (5^x-1) *5^1=5^x
Senior Manager
Joined: 05 Oct 2008
Posts: 258

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17 Nov 2008, 10:17
Thanks fresinha...
Intern
Joined: 19 Jun 2008
Posts: 20

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17 Nov 2008, 12:49
fresinha12 wrote:
study wrote:
How do you solve for this?

5^k - 5 ^k-1

Do not have the AC - only have the OA, will post it later.

5^(k-1)(5-1) =4*5^(k-1)

I don't understand where the (5-1) comes from...

I get it.. after 40 mins.. Jeez

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Re: Exponents   [#permalink] 17 Nov 2008, 12:49
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# [5 ^ k] - [5 ^ (k-1)]

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