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If a^6 - b^6 = 0, what is the value of a^3 - b^3? (1) b is

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Senior Manager
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If a^6 - b^6 = 0, what is the value of a^3 - b^3? (1) b is [#permalink]

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New post 07 Jun 2005, 02:20
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A
B
C
D
E

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If a^6 - b^6 = 0, what is the value of a^3 - b^3?

(1) b is greater than 1
(2) a is positive

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Director
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New post 07 Jun 2005, 03:38
sin e we have to find the value the answer to this is E

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Senior Manager
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Re: DS [#permalink]

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New post 07 Jun 2005, 07:40
cloudz9 wrote:
If a^6 - b^6 = 0, what is the value of a^3 - b^3?

(1) b is greater than 1
(2) a is positive


C.

using (1) and (2) we know that a^3 + b^3 is not zero. Hence a^3 - b^3 should be zero.

HMTG.

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Director
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New post 07 Jun 2005, 08:57
u r right since both a and b are +ve the value of a^3 - b^3 will always be zero

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New post 07 Jun 2005, 11:45
a^6 - b^6 = 0

implies (a^3+b^3)(a^3 - b^3) = 0

A &B are insufficient as knowing value of only 1 variable is not enough to show that (a^3+b^3) is +ve

C. both a,b >0
so
(a^3+b^3) >0
so
(a^3-b^3) must = 0

sifficient
_________________

ash
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I'm crossing the bridge.........

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New post 15 Jun 2005, 03:42
My answer is C.

Statement 1: Insufficent. A and D options are ruled out.
Stetament 2: Insufficient. B is ruled out.

Combined together, we conclude that A and B are both are positive hence a^3 + b^3 can not be zero. This forces a^3 - b^3 to be zero. Hence C.

Note : a^6 - b^6= (a^3 + b^3 ) (a^3 - b^3 )

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  [#permalink] 15 Jun 2005, 03:42
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If a^6 - b^6 = 0, what is the value of a^3 - b^3? (1) b is

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