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# if x is an integer, which value of x will yield the largest

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Current Student
Joined: 28 Dec 2004
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if x is an integer, which value of x will yield the largest [#permalink]

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31 Jul 2008, 10:42
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

if x is an integer, which value of x will yield the largest value for 5^-(x-3)^2

x= 3, -3, 9, -9, 0

Note: I saw something similar to this on my own exam..the numbers are made-up of course, the function is madeup also..just trying to test the concept..
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Joined: 30 Apr 2008
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Location: Oklahoma City
Schools: Hard Knocks

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31 Jul 2008, 10:50
I think the answer would be 3.

regardless of x being greater or less than 3, the - in the front will switch the sign after squaring and make the exponent negative for sure. So we will have $$\frac{1}{5^n}$$ where $$n = (x-3)^2$$

If x = 3, then we have -(3-3)^2, or 0^2 = 0, and -0 = 0, and so we then have $$\frac{1}{5^0} = 1/1 = 1$$.

Every other value listed for x will give an actual power making 5 * 5 * 5 * 5 or whatever that value becomes. With 5 being in the denominator, the largest fraction will be the one with the smallest denominator.

fresinha12 wrote:
if x is an integer, which value of x will yield the largest value for 5^-(x-3)^2

x= 3, -3, 9, -9, 0

Note: I saw something similar to this on my own exam..the numbers are made-up of course, the function is madeup also..just trying to test the concept..

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J Allen Morris
**I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$. GMAT Club Premium Membership - big benefits and savings Director Joined: 12 Jul 2008 Posts: 515 Schools: Wharton Re: exponent question [#permalink] ### Show Tags 31 Jul 2008, 10:51 fresinha12 wrote: if x is an integer, which value of x will yield the largest value for 5^-(x-3)^2 x= 3, -3, 9, -9, 0 Note: I saw something similar to this on my own exam..the numbers are made-up of course, the function is madeup also..just trying to test the concept.. If I'm reading this right 5^-(x-3)^2 = 1/(5^(x-3)^2) That means you're trying to minimize 5^(x-3)^2 And from that, you're trying to minimize |x-3| Of the answer choices, 3 would be the best choice. Intern Joined: 28 May 2008 Posts: 7 Re: exponent question [#permalink] ### Show Tags 31 Jul 2008, 10:52 I think answer is 3. 5^-(x-3)^2 => 1/5^(x-3)^2 1/5^(x-3)^2 => 3 makes the denominator 1 other values greater than 1. VP Joined: 17 Jun 2008 Posts: 1381 Re: exponent question [#permalink] ### Show Tags 31 Jul 2008, 11:01 fresinha12 wrote: if x is an integer, which value of x will yield the largest value for 5^-(x-3)^2 x= 3, -3, 9, -9, 0 Note: I saw something similar to this on my own exam..the numbers are made-up of course, the function is madeup also..just trying to test the concept.. to get the largest value of the function f(x)=5^-(x-3)^2 (x-3)^2 should be minimum.hence x=3 is the correct value _________________ cheers Its Now Or Never SVP Joined: 30 Apr 2008 Posts: 1874 Location: Oklahoma City Schools: Hard Knocks Re: exponent question [#permalink] ### Show Tags 31 Jul 2008, 11:01 mbathlagamt08 - Welcome to GMAT club! mbathlagmat08 wrote: I think answer is 3. 5^-(x-3)^2 => 1/5^(x-3)^2 1/5^(x-3)^2 => 3 makes the denominator 1 other values greater than 1. _________________ ------------------------------------ J Allen Morris **I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$.

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SVP
Joined: 07 Nov 2007
Posts: 1800
Location: New York

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31 Jul 2008, 11:28
fresinha12 wrote:
if x is an integer, which value of x will yield the largest value for 5^-(x-3)^2

x= 3, -3, 9, -9, 0

Note: I saw something similar to this on my own exam..the numbers are made-up of course, the function is madeup also..just trying to test the concept..

1) Largest value 5^-(x-3)^2 = when (x-3)^2 is least value..

(x-3) ^2 least value =0 --> when x=3.
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Current Student
Joined: 28 Dec 2004
Posts: 3357
Location: New York City
Schools: Wharton'11 HBS'12

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31 Jul 2008, 12:02
i agree with my example ans should be 3...

however on the exam..the ans choice listed didnt make (x-N)^2=0..i spent about 2 mins and just guessed..i think i was dubed by gmac..my exam was buggy..
SVP
Joined: 07 Nov 2007
Posts: 1800
Location: New York

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31 Jul 2008, 12:07
fresinha12 wrote:
i agree with my example ans should be 3...

however on the exam..the ans choice listed didnt make (x-N)^2=0..i spent about 2 mins and just guessed..i think i was dubed by gmac..my exam was buggy..

(x-N)^2=0 are you sure that power is 2 or -2 power.

(x-n)^-2 in this case.. answer could be different.
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Re: exponent question   [#permalink] 31 Jul 2008, 12:07
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