P 0.1 Stabilişti natura şsi suma seriilor: a) Σ 1 n\ ; b) Σ arctan 1 n# + n ...
P 0.1 Stabilişti natura şsi suma seriilor: a) Σ 1 n\ ; b) Σ arctan 1 n# + n ...
P 0.1 Stabilişti natura şsi suma seriilor: a) Σ 1 n\ ; b) Σ arctan 1 n# + n ...
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P 0.9 Fie (un) n 1 un ¸sir de numere reale strict pozitive ¸si un num¼ar<br />
real. Pentru …ecare num¼ar <strong>natura</strong>l n 1 punem<br />
n = un+1<br />
un<br />
n<br />
n + 1<br />
Ar¼ata¸ti c¼a:<br />
(i) Dac¼a > 1 ¸si exist¼a un num¼ar <strong>natura</strong>l n0 cu proprietatea c¼a<br />
atunci seria 1P<br />
n=1<br />
n 0; oricare ar … n n0;<br />
un este convergent¼a.<br />
(ii) Dac¼a 1 ¸si exist¼a un num¼ar <strong>natura</strong>l n0 cu proprietatea c¼a<br />
atunci seria 1P<br />
n=1<br />
n > 0; oricare ar … n n0;<br />
un este divergent¼a.<br />
P <strong>0.1</strong>0 Stabili¸ti <strong>natura</strong> <strong>seriilor</strong>:<br />
1X (2n 1)!! 1<br />
a)<br />
; b)<br />
(2n)!! 2n + 1<br />
n=1<br />
n=1<br />
1X<br />
n=1<br />
(2n 1)!!<br />
; c)<br />
(2n)!!<br />
P <strong>0.1</strong>1 Pentru …ecare a > 0; studia¸ti <strong>natura</strong> <strong>seriilor</strong>:<br />
1X<br />
1X<br />
n!<br />
a)<br />
; b) a<br />
a(a + 1)::: (a + n)<br />
n=1<br />
:<br />
1X<br />
n=1<br />
1 1<br />
(1+ +:::+ 2 n) ; c)<br />
P <strong>0.1</strong>2 Dac¼a ; ; ; x 2]0; +1[; stabili¸ti <strong>natura</strong> seriei<br />
1X ( + 1) ::: ( + n 1) ( + 1) ::: (<br />
( + 1) ::: ( + n 1)<br />
+ n 1)<br />
x n<br />
n=1<br />
(numit¼a seria hipergeometric¼a a lui Gauss) :<br />
P <strong>0.1</strong>3 S¼a se stabileasc¼a <strong>natura</strong> <strong>seriilor</strong>:<br />
1X<br />
1X<br />
a)<br />
c)<br />
1X<br />
n=1<br />
n=1<br />
( 1) n+1 (n + 1) n+1<br />
n n+2 ; b)<br />
( 1) n+1 2n + 1<br />
3 n ; d)<br />
f)<br />
1X<br />
n=1<br />
1X<br />
n=2<br />
n=1<br />
( 1) n+1 1<br />
p n (n + 1) ; g)<br />
( 1) n+1 1<br />
; e)<br />
ln n<br />
1<br />
n!<br />
1X<br />
n=1<br />
n<br />
e<br />
n<br />
:<br />
a n n!<br />
n n :<br />
( 1) n+1 n 1<br />
(n + 1)<br />
nn+1 ;<br />
3<br />
1X<br />
( 1)<br />
n=1<br />
n+1 1<br />
n(n + 1) ;<br />
1X<br />
( 1) n+1<br />
p<br />
n<br />
n + p 5 ;<br />
n=1