Can someone clarify the logic behind the given equation?Recurrence relation: verify that the expression given...
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Can someone clarify the logic behind the given equation?
Recurrence relation: verify that the expression given for $a_n$Could someone help me clarify the steps for this solution?What is the logic behind this sequence limit proof?Understanding how to use $epsilon-delta$ definition of a limitProof question about infinite seriesHow can I tell if the sequence re-cycles?Show convergence for $a_n = frac{a_{n-1}}{2} + 1$ with $a_0 = 0$Proving a sequence converges $epsilon-N$Proof that convergent sequence in $Bbb R$ is bounded.Given the following non-increasing sequences of sets…
$begingroup$
I have a question relating to image that I've attached. It is a proof that the sequence is increasing. I don't understand the logic behind the third equation $$frac{a_{n+1}}{a_n}>left (1-frac{1}{n+1}right ) left (frac{n+1}{n}right)$$
where does the equation in the first and second parenthesis come from?
Ok, I have another relating question:
why $frac{a_{n+1}}{a_n}> (1+frac{1}{n})$ ? ( The expression of third line).
[![
- enter image description here
]1]1
sequences-and-series limits eulers-constant
$endgroup$
add a comment |
$begingroup$
I have a question relating to image that I've attached. It is a proof that the sequence is increasing. I don't understand the logic behind the third equation $$frac{a_{n+1}}{a_n}>left (1-frac{1}{n+1}right ) left (frac{n+1}{n}right)$$
where does the equation in the first and second parenthesis come from?
Ok, I have another relating question:
why $frac{a_{n+1}}{a_n}> (1+frac{1}{n})$ ? ( The expression of third line).
[![
- enter image description here
]1]1
sequences-and-series limits eulers-constant
$endgroup$
add a comment |
$begingroup$
I have a question relating to image that I've attached. It is a proof that the sequence is increasing. I don't understand the logic behind the third equation $$frac{a_{n+1}}{a_n}>left (1-frac{1}{n+1}right ) left (frac{n+1}{n}right)$$
where does the equation in the first and second parenthesis come from?
Ok, I have another relating question:
why $frac{a_{n+1}}{a_n}> (1+frac{1}{n})$ ? ( The expression of third line).
[![
- enter image description here
]1]1
sequences-and-series limits eulers-constant
$endgroup$
I have a question relating to image that I've attached. It is a proof that the sequence is increasing. I don't understand the logic behind the third equation $$frac{a_{n+1}}{a_n}>left (1-frac{1}{n+1}right ) left (frac{n+1}{n}right)$$
where does the equation in the first and second parenthesis come from?
Ok, I have another relating question:
why $frac{a_{n+1}}{a_n}> (1+frac{1}{n})$ ? ( The expression of third line).
[![
- enter image description here
]1]1
sequences-and-series limits eulers-constant
sequences-and-series limits eulers-constant
edited 14 mins ago
Ieva Brakmane
asked 46 mins ago
Ieva BrakmaneIeva Brakmane
265
265
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3 Answers
3
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$begingroup$
From Bernoulli's inequality, we have
$$left( 1- frac{1}{(n+1)^2}right) > 1+(n+1) left(frac{-1}{(n+1)^2} right)=1-frac1{n+1}$$
Hence,
$$frac{a_{n+1}}{a_n}>left( 1- frac{1}{(n+1)^2}right)left( frac{n+1}{n}right)>left(1-frac1{n+1} right)left( frac{n+1}{n}right)$$
$endgroup$
add a comment |
$begingroup$
It is putting together the result from the first red box with the second one:
- $frac{a_{n+1}}{a_n} = color{blue}{left(1- frac{1}{(n+1)^2} right)^{n+1}}left( frac{n+1}{n}right)$
- $color{blue}{left(1- frac{1}{(n+1)^2} right)^{n+1}} > color{green}{1 + (n+1)left( frac{-1}{(n+1)^2}right)}$
$$Rightarrow frac{a_{n+1}}{a_n} > left(color{green}{1 + (n+1)left( frac{-1}{(n+1)^2}right)}right)left( frac{n+1}{n}right) = left(underbrace{1- frac{1}{n+1}}_{=frac{n}{n+1}}right)left( frac{n+1}{n}right)$$
$endgroup$
add a comment |
$begingroup$
So, we have
$$frac{a_{n+1}}{a_n} = left(1 - frac{1}{(n+1)^2}right)^{n+1}left(frac{n+1}{n}right).$$
The author then applies Bernoulli's inequality to the first term on the RHS:
$$left(1 - frac{1}{(n+1)^2}right)^{n+1} > 1 + (n+1)left(frac{-1}{(n+1)^2}right) = 1 - frac{1}{n+1}.$$
We can now return to the first equation and utilize this estimate; namely, we have
$$frac{a_{n+1}}{a_n} = left(1 - frac{1}{(n+1)^2}right)^{n+1}left(frac{n+1}{n}right) > left(1-frac{1}{n+1}right)left(frac{n+1}{n}right).$$
Finally, we multiply out the RHS of the inequality
$$frac{a_{n+1}}{a_n} > left(1-frac{1}{n+1}right)left(frac{n+1}{n}right) = frac{n+1}{n} - frac{1}{n} = 1.$$
So, we have
$$frac{a_{n+1}}{a_n} > 1 implies a_{n+1} > a_n,$$
which means that ${a_n}$ is an increasing sequence.
$endgroup$
add a comment |
Your Answer
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
From Bernoulli's inequality, we have
$$left( 1- frac{1}{(n+1)^2}right) > 1+(n+1) left(frac{-1}{(n+1)^2} right)=1-frac1{n+1}$$
Hence,
$$frac{a_{n+1}}{a_n}>left( 1- frac{1}{(n+1)^2}right)left( frac{n+1}{n}right)>left(1-frac1{n+1} right)left( frac{n+1}{n}right)$$
$endgroup$
add a comment |
$begingroup$
From Bernoulli's inequality, we have
$$left( 1- frac{1}{(n+1)^2}right) > 1+(n+1) left(frac{-1}{(n+1)^2} right)=1-frac1{n+1}$$
Hence,
$$frac{a_{n+1}}{a_n}>left( 1- frac{1}{(n+1)^2}right)left( frac{n+1}{n}right)>left(1-frac1{n+1} right)left( frac{n+1}{n}right)$$
$endgroup$
add a comment |
$begingroup$
From Bernoulli's inequality, we have
$$left( 1- frac{1}{(n+1)^2}right) > 1+(n+1) left(frac{-1}{(n+1)^2} right)=1-frac1{n+1}$$
Hence,
$$frac{a_{n+1}}{a_n}>left( 1- frac{1}{(n+1)^2}right)left( frac{n+1}{n}right)>left(1-frac1{n+1} right)left( frac{n+1}{n}right)$$
$endgroup$
From Bernoulli's inequality, we have
$$left( 1- frac{1}{(n+1)^2}right) > 1+(n+1) left(frac{-1}{(n+1)^2} right)=1-frac1{n+1}$$
Hence,
$$frac{a_{n+1}}{a_n}>left( 1- frac{1}{(n+1)^2}right)left( frac{n+1}{n}right)>left(1-frac1{n+1} right)left( frac{n+1}{n}right)$$
answered 39 mins ago
Siong Thye GohSiong Thye Goh
103k1468119
103k1468119
add a comment |
add a comment |
$begingroup$
It is putting together the result from the first red box with the second one:
- $frac{a_{n+1}}{a_n} = color{blue}{left(1- frac{1}{(n+1)^2} right)^{n+1}}left( frac{n+1}{n}right)$
- $color{blue}{left(1- frac{1}{(n+1)^2} right)^{n+1}} > color{green}{1 + (n+1)left( frac{-1}{(n+1)^2}right)}$
$$Rightarrow frac{a_{n+1}}{a_n} > left(color{green}{1 + (n+1)left( frac{-1}{(n+1)^2}right)}right)left( frac{n+1}{n}right) = left(underbrace{1- frac{1}{n+1}}_{=frac{n}{n+1}}right)left( frac{n+1}{n}right)$$
$endgroup$
add a comment |
$begingroup$
It is putting together the result from the first red box with the second one:
- $frac{a_{n+1}}{a_n} = color{blue}{left(1- frac{1}{(n+1)^2} right)^{n+1}}left( frac{n+1}{n}right)$
- $color{blue}{left(1- frac{1}{(n+1)^2} right)^{n+1}} > color{green}{1 + (n+1)left( frac{-1}{(n+1)^2}right)}$
$$Rightarrow frac{a_{n+1}}{a_n} > left(color{green}{1 + (n+1)left( frac{-1}{(n+1)^2}right)}right)left( frac{n+1}{n}right) = left(underbrace{1- frac{1}{n+1}}_{=frac{n}{n+1}}right)left( frac{n+1}{n}right)$$
$endgroup$
add a comment |
$begingroup$
It is putting together the result from the first red box with the second one:
- $frac{a_{n+1}}{a_n} = color{blue}{left(1- frac{1}{(n+1)^2} right)^{n+1}}left( frac{n+1}{n}right)$
- $color{blue}{left(1- frac{1}{(n+1)^2} right)^{n+1}} > color{green}{1 + (n+1)left( frac{-1}{(n+1)^2}right)}$
$$Rightarrow frac{a_{n+1}}{a_n} > left(color{green}{1 + (n+1)left( frac{-1}{(n+1)^2}right)}right)left( frac{n+1}{n}right) = left(underbrace{1- frac{1}{n+1}}_{=frac{n}{n+1}}right)left( frac{n+1}{n}right)$$
$endgroup$
It is putting together the result from the first red box with the second one:
- $frac{a_{n+1}}{a_n} = color{blue}{left(1- frac{1}{(n+1)^2} right)^{n+1}}left( frac{n+1}{n}right)$
- $color{blue}{left(1- frac{1}{(n+1)^2} right)^{n+1}} > color{green}{1 + (n+1)left( frac{-1}{(n+1)^2}right)}$
$$Rightarrow frac{a_{n+1}}{a_n} > left(color{green}{1 + (n+1)left( frac{-1}{(n+1)^2}right)}right)left( frac{n+1}{n}right) = left(underbrace{1- frac{1}{n+1}}_{=frac{n}{n+1}}right)left( frac{n+1}{n}right)$$
answered 34 mins ago
trancelocationtrancelocation
13.2k1827
13.2k1827
add a comment |
add a comment |
$begingroup$
So, we have
$$frac{a_{n+1}}{a_n} = left(1 - frac{1}{(n+1)^2}right)^{n+1}left(frac{n+1}{n}right).$$
The author then applies Bernoulli's inequality to the first term on the RHS:
$$left(1 - frac{1}{(n+1)^2}right)^{n+1} > 1 + (n+1)left(frac{-1}{(n+1)^2}right) = 1 - frac{1}{n+1}.$$
We can now return to the first equation and utilize this estimate; namely, we have
$$frac{a_{n+1}}{a_n} = left(1 - frac{1}{(n+1)^2}right)^{n+1}left(frac{n+1}{n}right) > left(1-frac{1}{n+1}right)left(frac{n+1}{n}right).$$
Finally, we multiply out the RHS of the inequality
$$frac{a_{n+1}}{a_n} > left(1-frac{1}{n+1}right)left(frac{n+1}{n}right) = frac{n+1}{n} - frac{1}{n} = 1.$$
So, we have
$$frac{a_{n+1}}{a_n} > 1 implies a_{n+1} > a_n,$$
which means that ${a_n}$ is an increasing sequence.
$endgroup$
add a comment |
$begingroup$
So, we have
$$frac{a_{n+1}}{a_n} = left(1 - frac{1}{(n+1)^2}right)^{n+1}left(frac{n+1}{n}right).$$
The author then applies Bernoulli's inequality to the first term on the RHS:
$$left(1 - frac{1}{(n+1)^2}right)^{n+1} > 1 + (n+1)left(frac{-1}{(n+1)^2}right) = 1 - frac{1}{n+1}.$$
We can now return to the first equation and utilize this estimate; namely, we have
$$frac{a_{n+1}}{a_n} = left(1 - frac{1}{(n+1)^2}right)^{n+1}left(frac{n+1}{n}right) > left(1-frac{1}{n+1}right)left(frac{n+1}{n}right).$$
Finally, we multiply out the RHS of the inequality
$$frac{a_{n+1}}{a_n} > left(1-frac{1}{n+1}right)left(frac{n+1}{n}right) = frac{n+1}{n} - frac{1}{n} = 1.$$
So, we have
$$frac{a_{n+1}}{a_n} > 1 implies a_{n+1} > a_n,$$
which means that ${a_n}$ is an increasing sequence.
$endgroup$
add a comment |
$begingroup$
So, we have
$$frac{a_{n+1}}{a_n} = left(1 - frac{1}{(n+1)^2}right)^{n+1}left(frac{n+1}{n}right).$$
The author then applies Bernoulli's inequality to the first term on the RHS:
$$left(1 - frac{1}{(n+1)^2}right)^{n+1} > 1 + (n+1)left(frac{-1}{(n+1)^2}right) = 1 - frac{1}{n+1}.$$
We can now return to the first equation and utilize this estimate; namely, we have
$$frac{a_{n+1}}{a_n} = left(1 - frac{1}{(n+1)^2}right)^{n+1}left(frac{n+1}{n}right) > left(1-frac{1}{n+1}right)left(frac{n+1}{n}right).$$
Finally, we multiply out the RHS of the inequality
$$frac{a_{n+1}}{a_n} > left(1-frac{1}{n+1}right)left(frac{n+1}{n}right) = frac{n+1}{n} - frac{1}{n} = 1.$$
So, we have
$$frac{a_{n+1}}{a_n} > 1 implies a_{n+1} > a_n,$$
which means that ${a_n}$ is an increasing sequence.
$endgroup$
So, we have
$$frac{a_{n+1}}{a_n} = left(1 - frac{1}{(n+1)^2}right)^{n+1}left(frac{n+1}{n}right).$$
The author then applies Bernoulli's inequality to the first term on the RHS:
$$left(1 - frac{1}{(n+1)^2}right)^{n+1} > 1 + (n+1)left(frac{-1}{(n+1)^2}right) = 1 - frac{1}{n+1}.$$
We can now return to the first equation and utilize this estimate; namely, we have
$$frac{a_{n+1}}{a_n} = left(1 - frac{1}{(n+1)^2}right)^{n+1}left(frac{n+1}{n}right) > left(1-frac{1}{n+1}right)left(frac{n+1}{n}right).$$
Finally, we multiply out the RHS of the inequality
$$frac{a_{n+1}}{a_n} > left(1-frac{1}{n+1}right)left(frac{n+1}{n}right) = frac{n+1}{n} - frac{1}{n} = 1.$$
So, we have
$$frac{a_{n+1}}{a_n} > 1 implies a_{n+1} > a_n,$$
which means that ${a_n}$ is an increasing sequence.
answered 20 mins ago
Gary MoonGary Moon
84116
84116
add a comment |
add a comment |
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