Prove that lim gn for n→∞ exists, and find it.

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In summary, the conversation is about proving the existence of a limit for a sequence given certain inequalities and finding the limit. The speaker also explains the rules of the forum and the purpose of helping with problems.
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dannysaf
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Suppose g1 , g2 ,... are any numbers that satisfy the inequalities
0 < gn < 1 and (1 − gn)gn+1 > 1/4 for all n.

Prove that lim gn for n→∞ exists, and find it.


I need well substantiated answer! Thanks.
 
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  • #2
dannysaf said:
I need well substantiated answer! Thanks.

Since you are pretty new to the forum, I'll explain some of the rules for you to understand how we operate. :)

If you're really looking for some "well substantiated answer" here, then, I'm very sorry to inform you that you've come to the wrong place. :( Don't miss the https://www.physicsforums.com/showthread.php?t=94383" that lie on top of every Homework Helping board. :)

We are here to guide you to tackle some problem, or to help you understand some concepts you find hard, and impossible to grasp. We, however, do not provide full solutions. Have you ever heard a saying

"Give a man a fish, and he'll eat for a day. But teach a man how to fish, he'll eat for a lifetime"?

The same rule applies here, providing complete solutions can trick both of you, and your professor into thinking that you have enough skill to solve the problem by yourself, while in fact, you don't. And what if you are in the exam room? Will there be anyone there to actually help you?

-------------------------------

Ok, so your sequence is obviously bounded:
0 < qn < 1.

Now, let's think about it, what if your sequence is monotonic? Then, it'll have limit as n tends to infinity, right?

So, let's try the following steps:
  • First, find some initial values of the sequence that satisfies the requirements.
  • Then, guess whether it's increasing or decreasing.
  • Finally, try to prove it. If you don't know where to start, then Proof by Contradiction is the way to go. :)
 
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1. What is a limit in calculus?

A limit in calculus is the value that a function approaches as its input (usually denoted as x) approaches a certain value. It is a fundamental concept in calculus and is used to analyze the behavior of functions as they approach specific values.

2. How do you prove that a limit exists?

To prove that a limit exists, you need to show that the function approaches a single value as the input approaches a specific value. This can be done by using the epsilon-delta definition of a limit, where you can manipulate inequalities to show that the distance between the function and the limit value approaches zero as the input approaches the specific value.

3. What does it mean for a limit to exist?

If a limit exists, it means that the function approaches a single value as the input approaches a specific value. In other words, the function has a well-defined value at that specific input, even if it is not defined at that point.

4. Why is it important to prove that a limit exists?

Proving that a limit exists is important because it allows us to evaluate the behavior of functions at specific points, even if the function is not defined at that point. It also helps us understand the continuity of a function and its behavior near certain points.

5. How do you find the limit of a function as n approaches infinity?

To find the limit of a function as n approaches infinity, you can use the following steps:
1. Rewrite the function in a way that allows you to evaluate it as n approaches infinity (e.g. by factoring or simplifying).
2. Plug in infinity for n and evaluate the function.
3. If the limit is an indeterminate form (e.g. 0/0 or ∞/∞), you can use techniques such as L'Hopital's rule or algebraic manipulation to evaluate the limit.
4. If the limit is a defined value, then that is the limit of the function. Otherwise, the limit does not exist.

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