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# can someone provide me with more info on this? i remember

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CEO
Joined: 21 Jan 2007
Posts: 2739
Location: New York City

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04 Oct 2007, 09:44
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

can someone provide me with more info on this? i remember learning this in high school but i look thru mgmat books and cannot find this concept.

Example

=5^k - 5^(k-1)
=5^k - (1/5)*5^k
CEO
Joined: 21 Jan 2007
Posts: 2739
Location: New York City

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04 Oct 2007, 09:52
=5^k - (1/5)*5^k
=5^k (1 - (1/5))
=5k*4/5
can we simplify the last step?
VP
Joined: 08 Jun 2005
Posts: 1145

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04 Oct 2007, 09:57
5^k - 5^(k-1)

lets assume k=3 then 5^3-5^2 = 125-25 = 100 hence:

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

or lets assume k=3

5^k-1 = 5^k/5

since

5^3-1 = 5^3/5 = 125/5 = 25 = 5^3-1 = 5^2

04 Oct 2007, 09:57
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