E:Personal computer users cannot literally be "in the beginning of a cycle when they." Perhaps their behavior is in the beginning of a cycle, but not they themselves.
解法如下:
the kth term of a certain sequence is given by (-1)^(k+1)乘以(1/2^k)
说明通项公式为:an=(-1)·(-1/2)^k
又因为K=10,已经是一个较大的数了,1-q^n,在n较大的情况下,是可以忽略的,因此
sn=a1/(1-q),代入即为:1/2除以1-(-1/2),答案为1/3.
production和收成比