【OG20-P279-312题】In any sequence of n nonzero numbers ,a pair of consecutive terns with opposite signs represents a sign change.For example,the sequence -2,3,-4,5 has three sign changes.Does the sequence of nonzero numbers S1,S2,S3..........Sn have an even number of sign changes?1.Sk=(-1)kfor all positive integers k from 1 to n.2.n is odd.
In the finite sequence of positive integers K1, K2, K3, . . . , K9, each term after the second is the sum of the two terms immediately preceding it. If K5 = 18, what is the value of K9 ? (1) K4 = 11 (2) K6 = 29