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

[SurekhaM988]

Hello,

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]

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.