Evaluate the limit of the sequence: $lim_{n_toinfty}frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot...
$begingroup$
Evaluate the limit of the sequence:
$$lim_{ntoinfty}frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})}$$
My try:
Stolz-cesaro: The limit of the sequence is $frac{infty}{infty}$
$$lim_{ntoinfty}frac{a_n}{b_n}=lim_{ntoinfty}frac{a_{n+1}-a_n}{b_{n+1}-b_n}$$
For our sequence:
$lim_{ntoinfty}frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})}=lim_{ntoinfty}frac{sqrt{n!}-sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})cdot(1+sqrt{n+1})-(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})}=lim_{ntoinfty}frac{sqrt{(n-1)!}cdot(sqrt{n-1})}{left((1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})right)cdot(sqrt{n}+1)}$
Which got me nowhere.
calculus sequences-and-series limits
$endgroup$
add a comment |
$begingroup$
Evaluate the limit of the sequence:
$$lim_{ntoinfty}frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})}$$
My try:
Stolz-cesaro: The limit of the sequence is $frac{infty}{infty}$
$$lim_{ntoinfty}frac{a_n}{b_n}=lim_{ntoinfty}frac{a_{n+1}-a_n}{b_{n+1}-b_n}$$
For our sequence:
$lim_{ntoinfty}frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})}=lim_{ntoinfty}frac{sqrt{n!}-sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})cdot(1+sqrt{n+1})-(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})}=lim_{ntoinfty}frac{sqrt{(n-1)!}cdot(sqrt{n-1})}{left((1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})right)cdot(sqrt{n}+1)}$
Which got me nowhere.
calculus sequences-and-series limits
$endgroup$
add a comment |
$begingroup$
Evaluate the limit of the sequence:
$$lim_{ntoinfty}frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})}$$
My try:
Stolz-cesaro: The limit of the sequence is $frac{infty}{infty}$
$$lim_{ntoinfty}frac{a_n}{b_n}=lim_{ntoinfty}frac{a_{n+1}-a_n}{b_{n+1}-b_n}$$
For our sequence:
$lim_{ntoinfty}frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})}=lim_{ntoinfty}frac{sqrt{n!}-sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})cdot(1+sqrt{n+1})-(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})}=lim_{ntoinfty}frac{sqrt{(n-1)!}cdot(sqrt{n-1})}{left((1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})right)cdot(sqrt{n}+1)}$
Which got me nowhere.
calculus sequences-and-series limits
$endgroup$
Evaluate the limit of the sequence:
$$lim_{ntoinfty}frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})}$$
My try:
Stolz-cesaro: The limit of the sequence is $frac{infty}{infty}$
$$lim_{ntoinfty}frac{a_n}{b_n}=lim_{ntoinfty}frac{a_{n+1}-a_n}{b_{n+1}-b_n}$$
For our sequence:
$lim_{ntoinfty}frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})}=lim_{ntoinfty}frac{sqrt{n!}-sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})cdot(1+sqrt{n+1})-(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})}=lim_{ntoinfty}frac{sqrt{(n-1)!}cdot(sqrt{n-1})}{left((1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})right)cdot(sqrt{n}+1)}$
Which got me nowhere.
calculus sequences-and-series limits
calculus sequences-and-series limits
asked Dec 12 '18 at 10:33
user605734 MBSuser605734 MBS
3029
3029
add a comment |
add a comment |
4 Answers
4
active
oldest
votes
$begingroup$
Consider:
$$
(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})
$$
Take the root from each pair of parentheses and multiply them, then:
$$
(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n}) > sqrt{n!} iff \
iff frac{1}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})} < frac{1}{sqrt{n!}}
$$
Going back to original we have that:
$$
frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})} le frac{sqrt{(n-1)!}}{sqrt{n!}} = frac{1}{sqrt n}
$$
But the function is greater than $0$ and hence using squeeze theorem we conclude that:
$$
0 le lim_{ntoinfty}x_n le lim_{ntoinfty}frac{1}{sqrt n} = 0
$$
Hence the limit is $0$.
$endgroup$
add a comment |
$begingroup$
$(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n}) ge sqrt{1}cdotsqrt{2}cdots sqrt{n}= sqrt{n!}$, hence
$0 le frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})} le frac{1}{sqrt{n}}.$
Can you proceed ?
$endgroup$
add a comment |
$begingroup$
Note that
$$
frac{sqrt{(n-1)!}}{prod_{k=1}^nbig(1+sqrt{k}big)}=frac{1}{1+sqrt{n}}
prod_{k=1}^{n-1}frac{sqrt{k}}{1+sqrt{k}}<frac{1}{1+sqrt{n}}to 0
$$
$endgroup$
add a comment |
$begingroup$
We have that
$$frac{sqrt{(n-1)!}}{prod_{k=1}^nbig(1+sqrt{k}big)}=frac1{sqrt n}prod_{k=1}^nfrac{sqrt{k}}{1+sqrt{k}}le frac1{sqrt n}$$
$endgroup$
$begingroup$
Elements on the denominator are multiplyting
$endgroup$
– user605734 MBS
Dec 12 '18 at 10:39
$begingroup$
Opssss....thanks!
$endgroup$
– gimusi
Dec 12 '18 at 10:40
add a comment |
Your Answer
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4 Answers
4
active
oldest
votes
4 Answers
4
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
Consider:
$$
(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})
$$
Take the root from each pair of parentheses and multiply them, then:
$$
(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n}) > sqrt{n!} iff \
iff frac{1}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})} < frac{1}{sqrt{n!}}
$$
Going back to original we have that:
$$
frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})} le frac{sqrt{(n-1)!}}{sqrt{n!}} = frac{1}{sqrt n}
$$
But the function is greater than $0$ and hence using squeeze theorem we conclude that:
$$
0 le lim_{ntoinfty}x_n le lim_{ntoinfty}frac{1}{sqrt n} = 0
$$
Hence the limit is $0$.
$endgroup$
add a comment |
$begingroup$
Consider:
$$
(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})
$$
Take the root from each pair of parentheses and multiply them, then:
$$
(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n}) > sqrt{n!} iff \
iff frac{1}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})} < frac{1}{sqrt{n!}}
$$
Going back to original we have that:
$$
frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})} le frac{sqrt{(n-1)!}}{sqrt{n!}} = frac{1}{sqrt n}
$$
But the function is greater than $0$ and hence using squeeze theorem we conclude that:
$$
0 le lim_{ntoinfty}x_n le lim_{ntoinfty}frac{1}{sqrt n} = 0
$$
Hence the limit is $0$.
$endgroup$
add a comment |
$begingroup$
Consider:
$$
(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})
$$
Take the root from each pair of parentheses and multiply them, then:
$$
(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n}) > sqrt{n!} iff \
iff frac{1}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})} < frac{1}{sqrt{n!}}
$$
Going back to original we have that:
$$
frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})} le frac{sqrt{(n-1)!}}{sqrt{n!}} = frac{1}{sqrt n}
$$
But the function is greater than $0$ and hence using squeeze theorem we conclude that:
$$
0 le lim_{ntoinfty}x_n le lim_{ntoinfty}frac{1}{sqrt n} = 0
$$
Hence the limit is $0$.
$endgroup$
Consider:
$$
(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})
$$
Take the root from each pair of parentheses and multiply them, then:
$$
(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n}) > sqrt{n!} iff \
iff frac{1}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})} < frac{1}{sqrt{n!}}
$$
Going back to original we have that:
$$
frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})} le frac{sqrt{(n-1)!}}{sqrt{n!}} = frac{1}{sqrt n}
$$
But the function is greater than $0$ and hence using squeeze theorem we conclude that:
$$
0 le lim_{ntoinfty}x_n le lim_{ntoinfty}frac{1}{sqrt n} = 0
$$
Hence the limit is $0$.
answered Dec 12 '18 at 10:52
romanroman
2,17321224
2,17321224
add a comment |
add a comment |
$begingroup$
$(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n}) ge sqrt{1}cdotsqrt{2}cdots sqrt{n}= sqrt{n!}$, hence
$0 le frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})} le frac{1}{sqrt{n}}.$
Can you proceed ?
$endgroup$
add a comment |
$begingroup$
$(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n}) ge sqrt{1}cdotsqrt{2}cdots sqrt{n}= sqrt{n!}$, hence
$0 le frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})} le frac{1}{sqrt{n}}.$
Can you proceed ?
$endgroup$
add a comment |
$begingroup$
$(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n}) ge sqrt{1}cdotsqrt{2}cdots sqrt{n}= sqrt{n!}$, hence
$0 le frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})} le frac{1}{sqrt{n}}.$
Can you proceed ?
$endgroup$
$(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n}) ge sqrt{1}cdotsqrt{2}cdots sqrt{n}= sqrt{n!}$, hence
$0 le frac{sqrt{(n-1)!}}{(1+sqrt{1})cdot(1+sqrt{2})cdot (1+sqrt{3})cdots (1+sqrt{n})} le frac{1}{sqrt{n}}.$
Can you proceed ?
answered Dec 12 '18 at 10:41
FredFred
45.7k1848
45.7k1848
add a comment |
add a comment |
$begingroup$
Note that
$$
frac{sqrt{(n-1)!}}{prod_{k=1}^nbig(1+sqrt{k}big)}=frac{1}{1+sqrt{n}}
prod_{k=1}^{n-1}frac{sqrt{k}}{1+sqrt{k}}<frac{1}{1+sqrt{n}}to 0
$$
$endgroup$
add a comment |
$begingroup$
Note that
$$
frac{sqrt{(n-1)!}}{prod_{k=1}^nbig(1+sqrt{k}big)}=frac{1}{1+sqrt{n}}
prod_{k=1}^{n-1}frac{sqrt{k}}{1+sqrt{k}}<frac{1}{1+sqrt{n}}to 0
$$
$endgroup$
add a comment |
$begingroup$
Note that
$$
frac{sqrt{(n-1)!}}{prod_{k=1}^nbig(1+sqrt{k}big)}=frac{1}{1+sqrt{n}}
prod_{k=1}^{n-1}frac{sqrt{k}}{1+sqrt{k}}<frac{1}{1+sqrt{n}}to 0
$$
$endgroup$
Note that
$$
frac{sqrt{(n-1)!}}{prod_{k=1}^nbig(1+sqrt{k}big)}=frac{1}{1+sqrt{n}}
prod_{k=1}^{n-1}frac{sqrt{k}}{1+sqrt{k}}<frac{1}{1+sqrt{n}}to 0
$$
answered Dec 12 '18 at 10:38
Yiorgos S. SmyrlisYiorgos S. Smyrlis
63.3k1384163
63.3k1384163
add a comment |
add a comment |
$begingroup$
We have that
$$frac{sqrt{(n-1)!}}{prod_{k=1}^nbig(1+sqrt{k}big)}=frac1{sqrt n}prod_{k=1}^nfrac{sqrt{k}}{1+sqrt{k}}le frac1{sqrt n}$$
$endgroup$
$begingroup$
Elements on the denominator are multiplyting
$endgroup$
– user605734 MBS
Dec 12 '18 at 10:39
$begingroup$
Opssss....thanks!
$endgroup$
– gimusi
Dec 12 '18 at 10:40
add a comment |
$begingroup$
We have that
$$frac{sqrt{(n-1)!}}{prod_{k=1}^nbig(1+sqrt{k}big)}=frac1{sqrt n}prod_{k=1}^nfrac{sqrt{k}}{1+sqrt{k}}le frac1{sqrt n}$$
$endgroup$
$begingroup$
Elements on the denominator are multiplyting
$endgroup$
– user605734 MBS
Dec 12 '18 at 10:39
$begingroup$
Opssss....thanks!
$endgroup$
– gimusi
Dec 12 '18 at 10:40
add a comment |
$begingroup$
We have that
$$frac{sqrt{(n-1)!}}{prod_{k=1}^nbig(1+sqrt{k}big)}=frac1{sqrt n}prod_{k=1}^nfrac{sqrt{k}}{1+sqrt{k}}le frac1{sqrt n}$$
$endgroup$
We have that
$$frac{sqrt{(n-1)!}}{prod_{k=1}^nbig(1+sqrt{k}big)}=frac1{sqrt n}prod_{k=1}^nfrac{sqrt{k}}{1+sqrt{k}}le frac1{sqrt n}$$
edited Dec 12 '18 at 10:45
answered Dec 12 '18 at 10:38
gimusigimusi
92.8k84494
92.8k84494
$begingroup$
Elements on the denominator are multiplyting
$endgroup$
– user605734 MBS
Dec 12 '18 at 10:39
$begingroup$
Opssss....thanks!
$endgroup$
– gimusi
Dec 12 '18 at 10:40
add a comment |
$begingroup$
Elements on the denominator are multiplyting
$endgroup$
– user605734 MBS
Dec 12 '18 at 10:39
$begingroup$
Opssss....thanks!
$endgroup$
– gimusi
Dec 12 '18 at 10:40
$begingroup$
Elements on the denominator are multiplyting
$endgroup$
– user605734 MBS
Dec 12 '18 at 10:39
$begingroup$
Elements on the denominator are multiplyting
$endgroup$
– user605734 MBS
Dec 12 '18 at 10:39
$begingroup$
Opssss....thanks!
$endgroup$
– gimusi
Dec 12 '18 at 10:40
$begingroup$
Opssss....thanks!
$endgroup$
– gimusi
Dec 12 '18 at 10:40
add a comment |
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