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If n is an integer and f(n) = f(n 1) n, what is the value of

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lyss3b
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If n is an integer and f(n) = f(n 1) n, what is the value of [#permalink] New post   15 Jun 2011, 15:30
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If n is an integer and f(n) = f(n – 1) – n, what is the value of f (4)?

(1) f(3) = 14

(2) f(6) = -1
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D
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Edvento
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Re: f(n) = f(n – 1) – n [#permalink] New post   18 Dec 2012, 00:46
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The equation says f(n) = f(n-1) - n
(1) states f(3)=14 and we need to find f(4)
so as per the equation, f(4) = f(4-1) -4
==> f(4)=f(3)-4
==> f(4)=14-4=10
So (1) is sufficient...Hope explanation for (2) is already clear. And this expalins the use of f(3)=14 as well.
So the answer is D
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Re: f(n) = f(n – 1) – n [#permalink] New post   15 Jun 2011, 16:16
f(4) = f(3) - 4

1) Sufficient, slot straights into above equation.

2)
f(6) = -1 = f(5) - 6
f(5) = 5 = f(4) - 5
f(4) = 10

Sufficient

D.
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Re: If n is an integer and f(n) = f(n – 1) – n, what is the [#permalink] New post   02 Aug 2012, 16:30
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If n is an integer and f(n) = f(n – 1) – n, what is the value of f (4)?

(1) f(3) = 14. Since f(n)=f(n-1)-n then: f(4)=f(3)-4 --> f(4)=14-4=10. Sufficient.

(2) f(6) = -1. The same way as above f(6)=f(5)-6 --> -1=f(5)-6 --> f(5)=5 --> f(5)=f(4)-5 --> 5=f(4)-5 --> f(4)=10. Sufficient.

Answer: D.

P.S. Please read carefully and follow: rules-for-posting-please-read-this-before-posting-133935.html
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Re: f(n) = f(n – 1) – n [#permalink] New post   17 Dec 2012, 21:55
pike wrote:
f(4) = f(3) - 4

1) Sufficient, slot straights into above equation.

2)
f(6) = -1 = f(5) - 6
f(5) = 5 = f(4) - 5
f(4) = 10

Sufficient

D.


I don't understand what you mean slot straights into above equation. When I simplify the f(3) I get -1 and for f(6) I also get -1. Is that why both are sufficient? I don't understand why Statement 1 the f(3)=14. What I supposed to do something else?
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Re: f(n) = f(n – 1) – n [#permalink] New post   17 Dec 2012, 22:25
dcastan2 wrote:
pike wrote:
f(4) = f(3) - 4

1) Sufficient, slot straights into above equation.

2)
f(6) = -1 = f(5) - 6
f(5) = 5 = f(4) - 5
f(4) = 10

Sufficient

D.


I don't understand what you mean slot straights into above equation. When I simplify the f(3) I get -1 and for f(6) I also get -1. Is that why both are sufficient? I don't understand why Statement 1 the f(3)=14. What I supposed to do something else?


Hii.
See the question gives us the relation: \(f(n)=f(n-1)-n\) and the question asks the value of \(f(4)\).

As per the above relation, if we expand \(f(4)\), we get: \(f(4)=f(3)-4\)---------[a]

Now coming to the statements:
Statement 1 gives us direct \(f(3)\). We just have to put in equation [a].
Statement 2 gives us \(f(6)=-1\).
\(f(6)\) can be expanded as \(f(5)\)-6. Moreover \(f(5)\) can be expanded as \(f(4)-5\). Put this value of \(f(5)\) in the former one. It will become \(f(6)=f(4)-9\), which will gives the value of \(f(4)\) as 10.

Both are sufficient.
Hope that helps.
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Re: f(n) = f(n – 1) – n [#permalink] New post   18 Dec 2012, 00:14
Marcab wrote:
dcastan2 wrote:
pike wrote:
f(4) = f(3) - 4

1) Sufficient, slot straights into above equation.

2)
f(6) = -1 = f(5) - 6
f(5) = 5 = f(4) - 5
f(4) = 10

Sufficient

D.


I don't understand what you mean slot straights into above equation. When I simplify the f(3) I get -1 and for f(6) I also get -1. Is that why both are sufficient? I don't understand why Statement 1 the f(3)=14. What I supposed to do something else?


Hii.
See the question gives us the relation: \(f(n)=f(n-1)-n\) and the question asks the value of \(f(4)\).

As per the above relation, if we expand \(f(4)\), we get: \(f(4)=f(3)-4\)---------[a]

Now coming to the statements:
Statement 1 gives us direct \(f(3)\). We just have to put in equation [a].
Statement 2 gives us \(f(6)=-1\).
\(f(6)\) can be expanded as \(f(5)\)-6. Moreover \(f(5)\) can be expanded as \(f(4)-5\). Put this value of \(f(5)\) in the former one. It will become \(f(6)=f(4)-9\), which will gives the value of \(f(4)\) as 10.

Both are sufficient.
Hope that helps.


Yes, thank you! But we don't use the =14 anywhere? What's the purpose of it then?
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Re: If n is an integer and f(n) = f(n 1) n, what is the value of [#permalink] New post   18 Dec 2012, 00:41
In statement 1, put f(3)=14. You will get the answer as 10.
In DS, if you know that with the given information a particular question can be solved then rather than trying to find the exact answer, move to the next statement.
In the explanation, I did the same.

Hope that helps.
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Re: If n is an integer and f(n) = f(n 1) n, what is the value of [#permalink] New post   07 Oct 2022, 17:32
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