请解释Prep 19, 41. Thanks!!! 19. 2463-!-item-!-187;#058&002761 For a finite sequence of nonzero numbers, the number of variations in sign is defined as the number of pairs of consecutive terms of the sequence for which the product of the two consecutive terms is negative. What is the number of variations in sign for the sequence 1, -3, 2, 5, -4, -6 ?
(A) One (B) Two (C) Three (D) Four (E) Five
the answer is C
41. 5676-!-item-!-187;#058&004686 All of the stocks on the over-the-counter market are designated by either a 4-letter or a 5-letter code that is created by using the 26 letters of the alphabet. Which of the following gives the maximum number of different stocks that can be designated with these codes?
(A) 2(26^5) (B) 26(26^4) (C) 27(26^4) (D) 26(26^5) (E) 27(26^5) the answer is C |