Re: 級數2
※ 引述《midarmyman (midarmyman)》之銘言：
: a_1=2
: a_n 1
: a_n+1=-------+-------
: 2 a_n
: a_n是數列
: show that the sequence is decreasing and bounded below.
: 我用數學歸納法 可是到最後a_n+2就不知道怎麼說他會小於a_n+1了
: 請指教 謝了
這樣不知道行不行
a_k恆>0
由算幾 a_k≧√2
a_n+1 1 1
-------- = --- + ------ ≦ 1
a_n 2 a_n^2
∴<a_n>遞減, 下界為√2
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