推 jamtu:用條件期望值去做，不過細節我忘了 09/15 23:51
→ a016258:在數學版回答了... 09/16 00:17
A fair coin is tossed until two tails occur successively.
Find the expected number of the tosses required.
Hint: Let
1 if the first toss result in tails.
X =
0 if the first toss result in heads.
and condition on X.
答案是 5
感謝幫忙回答的
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