Now that you’ve gotten a little more confident, we’re going to give you the opportunity to practice "without the training wheels

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问题 Now that you’ve gotten a little more confident, we’re going to give you the opportunity to practice "without the training wheels." When you want to check your work, you can turn to the solutions at the end. If you aren’t familiar with some of the mathematical concepts, make a note to pay particular attention to that chapter in this book; this practice set covers a wide range of topics tested on the GMAT.
   On all data sufficiency problems, the answer choices are the same (as you’ve learned). We’ve put them here for your reference.
   A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
   B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
   C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
   D. EACH statement ALONE is sufficient.
   E. Statements (1) and (2) TOGETHER are NOT sufficient.
What is the value of f2-g2?
   (1) f=-g+8
   (2) f=g-2

选项

答案C

解析 When we see a quadratic formula like f2-g2, we almost always want to simplify it to see its parts better. This formula simplifies into (f+g)(f-g), so if we can get values for each of those parenthetical statements, we can calculate the value of the whole. Statement (1) gives the value of f+g when it is rearranged, but doesn’t give the value of f-g. We can cross off A and D. Statement (2) gives the opposite: the value of f-g only. So it is not sufficient on its own--we can cross off B--but the two statements are sufficient together, so C is the correct answer.
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本试题收录于: GMAT QUANTITATIVE题库GMAT分类
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