Re: [計量] 小弟求幾題數學題感謝各位

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※ 引述《greatgun (槍王)》之銘言： : GWD 18-Q4 : If x and y are integers, what is the value of 2x^6y - 4 ? : (1) x^2y = 16 : (2) x^y = 4 : ANS: A (1) x^2y --> (x^2y)^3 = x^6y --> 2x^6y (以 DS 思路邏輯回答不去算數字) (2) 思路一樣答案應該為 D 吧? : GWD 18-Q6 : The function f is defined for each positive three-digit integer n by : f(n) = 2x 3y 5z, where x, y and z are the hundreds, tens, and units digits : of n, respectively. If m and v are three-digit positive integers such that : f(m) = 9 f(v), then m - v = : A. 8 : B. 9 : C. 18 : D. 20 : E. 80 : ANS: D 這題很棒在我的講義規類為函數題 + 指數題 + 位數題先弄清楚這函數是在幹什麼這函數是把三位數的百位數十位數個位數分別放在 2 的次方 3 的次方 5 的次方因為 f(m) 和 f(v) 差 9 所以 m 和 v 只差在十位數 (3 的次方) 且正好差 2 (3平方 = 9) 所以 m - v = 20 : GWD 18-Q9 : Is x < 0 ? : (1) x^3 < x^2 : (2) x^3 < x^4 : ANS: C (1) 兩邊同除 x^2 (必為正) --> x < 1 不可 (2) 同樣除 x^2 --> x < x^2 --> x^2 - x > 0, x(x-1) > 0 x > 1 or x < 0 --> 不可 (1) + (2) x < 0 (C) : GWD 18-Q29 : A sum of money was divided between John and Anne such that : the ratio of John's share to Anne's share was 5 to 3. : If John's share exceeded of the sum of money by $50, : (這句看不太懂) : what was Anne's share? : A. $180 : B. $270 : C. $340 : D. $450 : E. $720 : ANS: B 因為你漏打了 5/9 所以我也看不懂 John's share exceeded "5/9" of the sum of money by $50 John = 5k, Anne = 3k 5k - 5/9(8k) = 50 (5/9)k = 50 k = 90 Anne = 270 : GWD 18-Q32 : What is the probability that event E or event F or both will occur? : (1) The probability that event E will occur is 0.6. : (2) The probability that event F will occur is 0.4. : ANS: E P(E or F) = P(E) + P(F) - P(E&F) 從頭到尾都沒有 P(E&F) (Both Occur) 所以 (E) : GWD 18-Q36 : If x and y are integers, is y an even integer? : (1) 2y - x = x^2 - y^2 : (2) x is an odd integer. : ANS: A 做奇數偶數題就是要勇敢狠狠的刪等號兩邊的東西 (1) -x 和 x^2 奇偶性相同請同時刪掉 2y = -y^2, 很明顯 y 是偶數 (可以為負) (2) x 看不出 y 有啥關係 : 抱歉各位大大!小弟因為沒補習一直埋頭苦幹可是還是有很多不會 : 所以只能靠版上的各位大大相助。感謝再感謝 -- 每月專修及機經家教課程開跑幫助各位複習數學更有效率更確實 GMAT SAT 留學考試 - 勇闖夢想的新鮮人 http://ndxica.pixnet.net/blog -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 111.248.202.78

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greatgun

10/01 21:24, , 1^F

10/01 21:24, 1^F

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