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But there’s something in me that just keeps going on. I think it has something to do with tomorrow, that there is always one, and that everything can change when it comes. http://aimingformba.blogspot.com

If \(a<0\) it must be true that \(-a=b-c\); If \(a\geq{0}\) it must be true that \(a=b-c\).

(1) \(c=a+b\) --> \(-a=b-c\). But we don't know whether \(a<0\). Not sufficient. (2) \(a<0\). Question becomes is \(-a=b-c\)? We don't know that. Not sufficient.

(1)+(2) Form 2: \(a<0\), question becomes is \(-a=b-c\)? Statement 1 confirms this. Sufficient.

Re: Is a = b c? (1) c = a + b (2) a < 0 [#permalink]

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10 Oct 2012, 11:06

Is this approach correct?

For ┃a┃ = b – c to be true , (b - c ) >=0 ie positive

(1) c = a + b : for (b - c ) >=0 to be true a needs to be <=0. Not given, hence insufficient (2) a < 0, says nothing about (b - c ) >=0 Hence insufficient (1)+(2) proves b - c>=0. Sufficient.

Re: Is a = b c? (1) c = a + b (2) a < 0 [#permalink]

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24 May 2016, 14:12

Hi Bunuel Actually, I did not understand the concept of statement 2 confirms statement 1. if the two statements confirmed each other, it means that answer C. please clarify more regarding the concept. I always fall in the traps of absolute value DS questions.

Re: Is a = b c? (1) c = a + b (2) a < 0 [#permalink]

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22 Sep 2016, 21:59

Hi Bunuel, I know this is an old question, but if statement 2 says a is negative can we not answer it because we plug the negative a back into the absolute value in the stem? My thought was that since lal=b-c is either a=b-c or -a=c-b we could say b is sufficient since statement 2 says a is negative. I just don't fully understand the concept.

Hi Bunuel, I know this is an old question, but if statement 2 says a is negative can we not answer it because we plug the negative a back into the absolute value in the stem? My thought was that since lal=b-c is either a=b-c or -a=c-b we could say b is sufficient since statement 2 says a is negative. I just don't fully understand the concept.

The question asks: Is ┃a┃ = b – c.

From (2) we know that a is negative. How this can be sufficient to answer the question whether┃a┃ = b – c?
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