Greatest integer function limit problem. Proving whether the limit exists

In summary, the conversation discusses the process of proving the existence of a limit and a possible solution using the right and left limits, with the conclusion that the limit exists. There is also a request for clarification on the meaning of [[x]].
  • #1
johnjrgs
1
0

Homework Statement


Prove that the limit exists.
lim 5 - 1/2[[2x]]
x-->1
Show your solution..

Homework Equations





The Attempt at a Solution


Tried getting the limit from the right and left.. not sure if what I've done is right though but this is what I got.

lim 5 - 1/2[[2x]] ===> 5-1/2(2(1)) ====> 4
x-->1+

lim 5 - 1/2[[2x]] ===> 5-1/2(2(1)) ====> 4
x-->1-

The answer I got is equal in both ways, therefore the limit exists.

If I'm wrong tell me where and help me please.
 
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  • #2
It would help if you told us what [[x]] meant! I thought it might be the "floor function" but if that were true then for 0< x< 1, [[2x]] would be 0, not 2, so the lower limit would be 5, not 4.
 

1. What is the greatest integer function?

The greatest integer function, denoted as floor or ⌊x⌋, is a mathematical function that rounds down a real number to the nearest integer. For example, ⌊3.8⌋ = 3 and ⌊-2.5⌋ = -3.

2. What is a limit in calculus?

In calculus, a limit is the value that a function approaches as the input (or independent variable) gets closer and closer to a specific value. It is denoted as lim and is used to describe the behavior of a function near a certain point.

3. What is the limit of the greatest integer function?

The limit of the greatest integer function at a specific point, say x = a, is the greatest integer less than or equal to a. This means that the limit of ⌊x⌋ as x approaches a is equal to ⌊a⌋.

4. How do you prove the existence of a limit for the greatest integer function?

In order to prove the existence of a limit for the greatest integer function, we need to show that the limit from the left and the limit from the right are equal. This means that as x approaches the specific point from the left and from the right, the values of ⌊x⌋ approach the same value. If this is the case, then we can say that the limit exists.

5. Can the limit of the greatest integer function be undefined?

Yes, the limit of the greatest integer function can be undefined. This happens when the limit from the left and the limit from the right are not equal. In this case, we say that the limit does not exist for that specific point.

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