1。Let M be the maximum value and N be the minimum value of the expression (X^2+Y)/ Y. If a<=X<=b and c<=Y<=d then what is the value of M - N? (1) c = 3 (2) a = -2, b = 5 and d = 7 答案是B(2单独成立),解释说In order to find the minimum, if x could equal 0 (implied by its range covering both negative and positive number), then we know the minimum of the expression too: no matter what y equals, the result will be 1. 我的问题,要是Y< 0 ,式子值不就小于1了吗?怎么会和Y的最小值d 没有关系呢?? 不明白。。。 2。 Set B has three positive integers with a median of 9. If the largest possible range of the three numbers is 19, given a certain mean, what is that mean? (A) 22 (B) 10 (C) 9.6 (D) 9 (E) It cannot be determined from the information given 答案是B 为什么不是E,有很多可能啊?!! 附件中是带详细讲解的PR Hard Math,解释在每篇题的下面,CD好像找不到了,刚发了份在下载区,顺带也放在这~ |