GRE考试

【单选题】If r=-2 and p＜0, which of the following has the least value
A、4pr²
B、2pr³
C、-2pr⁴
D、-4pr⁵
E、-6pr⁶
网考网参考答案：D
网考网解析：
You are given that r=-2. Therefore, the best approach to solving this problem is to replace r with-2 in each of the answer choices, as follows: Answer choice A: 4pr 2 =4p(-2) 2 , which equals (4)(4)p, or 16p. Answer choice B: 2pr 3 =2p(-2) 3 , which equals (2)(-8)p, or -16p. Answer choice C: -2pr 4 =-2p(-2)4, which equals (-2)(16)p, or -32p. Answer choice D: -4pr 5 =-4p(-2) 5 , which equals (-4)(-32)p, or 128p. Answer choice E: -6pr 6 =-6p(-2) 6 , which equals (-6)(64)p, or -384p. The question asks for the least value. You are given that p＜0, which means that p is a negative number. If you substitute any negative number into the results obtained above, only answer choices A and D will yield a negative value. Therefore, you can eliminate answer choices B, C, and E, because they will all be larger than either answer choice A or D. When p＜0, 128p will always be less than 16p, so answer choice D is correct. Alternatively, if you recognize that a negative number raised to an odd number remains negative, then only answer choice D will yield a negative number: -4×p (another negative number)×r 5 (another negative number)=a negative number. All of the other answer choices would yield a positive number, so answer choice D must have the least value. document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>