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Post subject: GRE Algebra (Quantitative Comparison) Posted: Sat Mar 31, 2012 9:22 am 

Joined: Sun May 30, 2010 3:15 am Posts: 424

Quantity A: (5x² – 20)/(x – 2) Quantity B: 4x + 8
A. Quantity A is greater. B. Quantity B is greater. C. The two quantities are equal. D. The relationship cannot be determined from the information given.
The correct answer is (D). To solve this, you must simplify Quantity A. Factor the common 5 in the numerator to make 5(x² – 4)/(x – 2) and then factor the difference of squares in the numerator: 5(x – 2)(x + 2)/(x – 2). Now you can cancel out the (x – 2) from both the numerator and denominator to get 5(x + 2).
Factor 4 in Quantity B. It becomes 4(x + 2).
Now we see that the both quantities have the same factor, (x + 2), which becomes 0 if x = 2. In this case quantities will be equal. However, if (x + 2) is positive, then quantity A will be greater because 5 > 4. We already have two different possibilities, so the relationship cannot be determined from the information given. The correct answer is D.  Can't you divide both quantities by (x + 2) so that A = 5 and B = 8?


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Gennadiy

Post subject: Re: t.1, s.2, qt.7: algebra, manipulating expressions Posted: Sat Mar 31, 2012 9:32 am 

Joined: Sun May 30, 2010 2:23 am Posts: 498


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