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Re: a is a nonzero integer. Is a^a greater than 1? [#permalink]
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Hi 23a2012,

Unfortunately, that's NOT how the math "works"

When dealing with a negative exponent, you have to put the entire calculation "under" the 1.

With your example, we have (-2)^(-2). This can be rewritten as....

1/[(-2)^2] = 1/4

IF....we were dealing with (-3)^(-3) though, we'd have.....

1/[(-3)^3] = 1/-27 = -1/27

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Re: a is a nonzero integer. Is a^a greater than 1? [#permalink]
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Hi 23a2012,

If you have an EVEN exponent, then you CANNOT have a negative outcome (unless the negative "sign" is "outside" of the exponent, and thus unaffected by the exponent).

eg
(2)^2 = 4
(2)^(-2) = 1/4

(-2)^(2) = 4
(-2)^-(2) = 1/4

(-1)[2^(-2)] = (-1)[1/4] = -1/4

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a is a nonzero integer. Is a^a greater than 1? [#permalink]
Bunuel wrote:
a is a nonzero integer. Is a^a greater than 1?

(1) a < -1. So, a could be -2, -3, -4, ... If a is a negative even integer, then a^a will be a positive fraction less than 1 (for example, if a = -2, then a^a = (-2)^(-2) = 1/4) and if a is a negative odd integer, then a^a will be a negative fraction greater than -1 (for example, if a = -3, then a^a = (-3)^(-3) = -1/27). In any case the result is less than 1. Sufficient.

(2) a is even. If a = 2, then a^a = 4 > 1 but if a = -2, then a^a = 1/4 < 1. Not sufficient.

Answer: A.

Hope it's clear.



Dear Bunuel, I think that (-2)^(-2) which is -1/2^2 should be negative fraction less than 1 and equal to = (- 1/4 )
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a is a nonzero integer. Is a^a greater than 1? [#permalink]
EMPOWERgmatRichC wrote:
Hi 23a2012,

Unfortunately, that's NOT how the math "works"

When dealing with a negative exponent, you have to put the entire calculation "under" the 1.

With your example, we have (-2)^(-2). This can be rewritten as....

1/[(-2)^2] = 1/4

IF....we were dealing with (-3)^(-3) though, we'd have.....

1/[(-3)^3] = 1/-27 = -1/27

GMAT assassins aren't born, they're made,
Rich

Ok, can you tell me how write -1/4 in the form a^a
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Re: a is a nonzero integer. Is a^a greater than 1? [#permalink]
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23a2012 wrote:
Bunuel wrote:
a is a nonzero integer. Is a^a greater than 1?

(1) a < -1. So, a could be -2, -3, -4, ... If a is a negative even integer, then a^a will be a positive fraction less than 1 (for example, if a = -2, then a^a = (-2)^(-2) = 1/4) and if a is a negative odd integer, then a^a will be a negative fraction greater than -1 (for example, if a = -3, then a^a = (-3)^(-3) = -1/27). In any case the result is less than 1. Sufficient.

(2) a is even. If a = 2, then a^a = 4 > 1 but if a = -2, then a^a = 1/4 < 1. Not sufficient.

Answer: A.

Hope it's clear.



Dear Bunuel, I think that (-2)^(-2) which is -1/2^2 should be negative fraction less than 1 and equal to = (- 1/4 )


hi ,
-2^-2= 1/(-2)^2=1/4....
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Re: a is a nonzero integer. Is a^a greater than 1? [#permalink]
Bunuel wrote:
a is a nonzero integer. Is a^a greater than 1?

(1) a < -1. So, a could be -2, -3, -4, ... If a is a negative even integer, then a^a will be a positive fraction less than 1 (for example, if a = -2, then a^a = (-2)^(-2) = 1/4) and if a is a negative odd integer, then a^a will be a negative fraction greater than -1 (for example, if a = -3, then a^a = (-3)^(-3) = -1/27). In any case the result is less than 1. Sufficient.

(2) a is even. If a = 2, then a^a = 4 > 1 but if a = -2, then a^a = 1/4 < 1. Not sufficient.

Answer: A.

Hope it's clear.


Hi Bunuel, But the question is if a^a is greater than 1 (not less than 1).In such a case, don't we need both ST-1 and ST-2 to answer the question?
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Re: a is a nonzero integer. Is a^a greater than 1? [#permalink]
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FANewJersey wrote:
Bunuel wrote:
a is a nonzero integer. Is a^a greater than 1?

(1) a < -1. So, a could be -2, -3, -4, ... If a is a negative even integer, then a^a will be a positive fraction less than 1 (for example, if a = -2, then a^a = (-2)^(-2) = 1/4) and if a is a negative odd integer, then a^a will be a negative fraction greater than -1 (for example, if a = -3, then a^a = (-3)^(-3) = -1/27). In any case the result is less than 1. Sufficient.

(2) a is even. If a = 2, then a^a = 4 > 1 but if a = -2, then a^a = 1/4 < 1. Not sufficient.

Answer: A.

Hope it's clear.


Hi Bunuel, But the question is if a^a is greater than 1 (not less than 1).In such a case, don't we need both ST-1 and ST-2 to answer the question?


The question asks: is a^a > 1.

From (1) we get that if a < -1, (if a is -2, -3, -4, ... ) a^a < 1. So, we have a definite NO answer to the question. Recall that a definite NO to an YES/NO DS questions is sufficient the same way as a definite YES is.
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Re: a is a nonzero integer. Is a^a greater than 1? [#permalink]
NoHalfMeasures wrote:
a is a nonzero integer. Is a^a greater than 1?

(1) a < -1
(2) a is even


Titans are here but here are my two cents.

Is a^a greater than 1? so your answer should be yes or no
now

(1) a<-1 => a can be -2,-3,-4,.... a^a for a=-2 => (-2)^(-2)=1/(-2)^2=1/4 which is less than one.for rest of the values the denominator will be even bigger so we can say NO hence SUFFICIENT

(2) a is even so it can be anything 2,-2,4,-4,6,-6... we already know that statement isn't true for -ve values for positive value answer is yes =>2^2>1
SO there are 2 answers YES and NO hence NOT SUFFICIENT

ANSWER A
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Re: a is a nonzero integer. Is a^a greater than 1? [#permalink]
a is a nonzero integer. Is \(a^a\) greater than 1?

(1) \(a < -1\)

if \(a = -2\)

\(-2^{-2} = \frac{1}{4}\)
\(-3^{-3} = \frac{-1}{27}\)

a^a is not greater than 1. Sufficient.

(2) a is even

\(2^2\) = 4. Greater than 1
\(-2^{-2}\) = not greater than 1.

Answer is A.
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Re: a is a nonzero integer. Is a^a greater than 1? [#permalink]
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