[求助]prep里的一道数学题

ada3063

For a finite sequence of nonzero numbers, the number of variation 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 sigh for sequence 1. -3,2,5,-4.-6

答案是three

但是我连题目都看不懂。。。完全不知道这道题要我干吗？

望解释

谢谢

jh1904

两两相乘，乘积为负的就是一次 variation in sign。1*-3=-3, -3*2=-6, 2*5=10, 5*-4=-20, -4*-6=24, 所一答案是3。

ada3063

原来如此，谢谢

ledazhou

当时做的时候也楞了半天，不过慢慢冷静一下分析一下语句就可以了。 考试时千万要冷静。。