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# ab = 0?

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Joined: 05 Nov 2010
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07 Nov 2010, 13:49
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55% (hard)

Question Stats:

54% (02:24) correct 46% (01:13) wrong based on 117 sessions

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ab = 0?

(1) a + b + ab = 0
(2) a - b = 0
[Reveal] Spoiler: OA
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07 Nov 2010, 14:17
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Expert's post
Creeper300 wrote:
ab=0?

1. a+b+ab=0
2. a-b=0

(1) a+b+ab=0 --> if both unknowns equal to zero then the answer will be YES but if a=1 and b=-1/2 then the answer will be NO. Not sufficient.
(2) a=b. Clearly insufficient.

(1)+(2) a+b+ab=0 --> as a=b then a+b+ab=b+b+b^2=2b+b^2=0 --> b(2+b)=0 --> either b=a=0 and the answer will be YES or b=a=-2 and the answer will be NO. Not sufficient.

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22 Jan 2015, 10:56
Hello from the GMAT Club BumpBot!

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22 Jan 2015, 22:45
Expert's post
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Creeper300 wrote:
ab = 0?

(1) a + b + ab = 0
(2) a - b = 0

Is ab = 0?
implies Is either a or b or both = 0? i.e. is it necessary that at least one of them has to be 0?

(1) a + b + ab = 0

a(1+b) = -b
a = -b/(1+b)
If b = 0, a = 0
If b = 1, a = -1/2
So ab may or may not be 0. Not sufficient.

(2) a - b = 0
a = b
If a = 0, b = 0
If a = 5, b = 5
So ab may or may not be 0. Not sufficient.

Using both, a + a + a^2 = 0
2a + a^2 = 0
a(2+a) = 0
So either a = 0 (so b = 0) or a = -2 (so b = -2)
In first case, ab = 0. In second case ab = 4.
So ab may or may not be 0. Not sufficient.

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28 May 2016, 07:10
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: ab = 0?   [#permalink] 28 May 2016, 07:10
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