[考古] 98台大(B)第五題

[henry9621205 (清心小子)]

00
Σ {[(2^(1/2)-2(1/3)] [(2^(1/2)-2^(1/4)]........[(2^(1/2)-2^(1/n)]}
n=3

判歛散?


謝謝!!

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推 midarmyman:divergent. by n-th test
推 midarmyman:不然也可以 原式>sigma(2^(1/2)-1)^(
→ midarmyman:n-2) n from 0 to infinity
推 CDnow:可是我用ratio test是<1 convergent
→ owlran:樓上算出來是根號2-1嘛 ..
推 CDnow:嗯
推 lovekwen:本題convergent 用ratio test最明顯
推 midarmyman:應該收斂財對 我根號二減一看錯