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# When [k^n-1]/[k-1]=k^n-1+k^n-2+.....+k+1,

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Intern
Joined: 11 Nov 2019
Posts: 11

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Updated on: 19 Nov 2019, 22:47
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When [k^(n-1)]/[k-1]=k^(n-1)+k^(n-2)+.....+k+1, 7^8+7^7+.....+1= 6,725,601, what is the value of 7^9?

A. 6*6,725,601 + 1 B. 6*6,725,601 -1 C. 5*6,725,601 +1 D. 5*6,725,601 -1 E. 7*6,725,601+1

Hello all!
There is this sequence problem I can't figure out a solution to.
Can someone share any easy way to solve it?
Thanks!

Originally posted by ec9rs on 19 Nov 2019, 18:36.
Last edited by ec9rs on 19 Nov 2019, 22:47, edited 2 times in total.
Math Expert
Joined: 02 Aug 2009
Posts: 8281

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19 Nov 2019, 20:23
ec9rs wrote:
When [k^n-1]/[k-1]=k^n-1+k^n-2+.....+k+1, 7^8+7^7+.....+1= 6,725,601, what is the value of 7^9?

A. 6*6,725,601 + 1 B. 6*6,725,601 -1 C. 5*6,725,601 +1 D. 5*6,725,601 -1 E. 7*6,725,601+1

Hello all!
There is this sequence problem I can't figure out a solution to.
Can someone share any easy way to solve it?
Thanks!

The question has asked o be posted clearly and formatted too.
It is not clear whether $$k^{n-1}/(k-1)$$ or $$k^n-1/(k-1)$$
_________________
Intern
Joined: 11 Nov 2019
Posts: 11

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19 Nov 2019, 20:50
chetan2u wrote:
ec9rs wrote:
When [k^n-1]/[k-1]=k^n-1+k^n-2+.....+k+1, 7^8+7^7+.....+1= 6,725,601, what is the value of 7^9?

A. 6*6,725,601 + 1 B. 6*6,725,601 -1 C. 5*6,725,601 +1 D. 5*6,725,601 -1 E. 7*6,725,601+1

Hello all!
There is this sequence problem I can't figure out a solution to.
Can someone share any easy way to solve it?
Thanks!

The question has asked o be posted clearly and formatted too.
It is not clear whether $$k^{n-1}/(k-1)$$ or $$k^n-1/(k-1)$$

Hi! Sorry for the confusion!
I edited the original post and it is supposed to be $$k^{n-1}/(k-1)$$ .
Thanks!
Math Expert
Joined: 02 Sep 2009
Posts: 59587

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19 Nov 2019, 22:58
ec9rs wrote:
When [k^(n-1)]/[k-1]=k^(n-1)+k^(n-2)+.....+k+1, 7^8+7^7+.....+1= 6,725,601, what is the value of 7^9?

A. 6*6,725,601 + 1 B. 6*6,725,601 -1 C. 5*6,725,601 +1 D. 5*6,725,601 -1 E. 7*6,725,601+1

Hello all!
There is this sequence problem I can't figure out a solution to.
Can someone share any easy way to solve it?
Thanks!

THE TOPIC IS LOCKED AND ARCHIVED.
_________________
Re: When [k^n-1]/[k-1]=k^n-1+k^n-2+.....+k+1,   [#permalink] 19 Nov 2019, 22:58
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