algebra

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algebra

by sud21 » Sat Jan 28, 2012 11:40 pm
Is absolute value of (X-4)*(X-7) equal to X^2-11X+28?
1). X>4
2). X>7
Source: — Data Sufficiency |

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by Anurag@Gurome » Sat Jan 28, 2012 11:50 pm
sud21 wrote:Is absolute value of (X-4)*(X-7) equal to X^2-11X+28?
1). X>4
2). X>7
|(x - 4)*(x - 7)| = |x - 4|*|x - 7|

Statement 1: x > 4 --> |x - 4| = (x - 4)
Now if x = 7, then the product will be zero, otherwise it will have some other value.

Not sufficient

Statement 2: As x > 7, x must be greater than 4 too.
Hence, |x - 4| = (x - 4) and |x - 7| = (x - 7)
Hence, their product will also have a specific expression. And we can answer the question in yes or no.

Sufficient

The correct answer is B.
Last edited by Anurag@Gurome on Sun Jan 29, 2012 3:16 am, edited 1 time in total.
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by Prashant Ranjan » Sun Jan 29, 2012 3:13 am
Pardon me if i am mistaken.

If (2) says x>7 then |(x-4)*(x-7)| = (x-4)*(x-7)
(Since x>7 so |x-7| = x-7 and |x-4| = x-4

So I think shouldn't the answer be B (as the second condition alone is sufficient?).

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by Anurag@Gurome » Sun Jan 29, 2012 3:15 am
Prashant Ranjan wrote:Pardon me if i am mistaken.

If (2) says x>7 then |(x-4)*(x-7)| = (x-4)*(x-7)
(Since x>7 so |x-7| = x-7 and |x-4| = x-4
Thanks for pointing it out.
Editing the reply.
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