| easier way |
| 送交者: 车五进二 2019月11月25日14:15:04 于 [灵机一动] 发送悄悄话 |
| 回 答: n=182 由 zhf 于 2019-11-25 12:07:40 |
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Let P(n) be the probability that after n moves, the bug went back to A. Then P(n) = (1 - P(n-1))/3, with P(1) = 0. You can use the recursive formula to find P(7). Alternatively, solve the recursion to obtain P(n) = (1-(-3)^(1-n))/4 |
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