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Help needed - algebra-guide 2-page 89-problem 5

by SurekhaM988 Mon Jan 01, 2018 5:56 pm


I need help with the following question (As listed in Guide 2-Page 89- Chapter 6- Question 5 )

What is x?
1) x = 4y-4
2) xy =8

Answer is E. I am having a hard time understanding the answer. I expected it to be C as you can get x as {-8,4} and you have a quadratic equation which is not a perfect square. Please help.
Sage Pearce-Higgins
ManhattanGMAT Staff
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Joined: Thu Apr 03, 2014 4:04 am

Re: Help needed - algebra-guide 2-page 89-problem 5

by Sage Pearce-Higgins Mon Jan 08, 2018 6:03 am

In Data Sufficiency questions, if a piece of information gives two possible answers to the question, then it is not sufficient. Knowing from both statements that x is either -8 or 4 means that we don't have a single value for x, and therefore the information is not sufficient. Sure, I know that we've narrowed down the answers somewhat, but it's one of the rules of GMAT Data Sufficiency that we're looking for a single definitive answer.