Example of Function f:R-R where lim x→0 xf(1/x) ≠ 0

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In summary, the conversation discusses finding an example of a function f:R-R where the limit of xf(1/x) as x approaches zero is not zero. It is suggested that f(1/x) can cancel out the x, making the limit independent of x. The question then arises of what f(x) would need to be for f(1/x) to be proportional to 1/x. A hint is given to relabel 1/x as "lambda" and use this to find the answer.
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Please help with the following problem:

Find an example of a finction f:R-R where

lim x tends towards zero of xf(1/x) is not zero
 
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It would obviously be the case when f(1/x) can cancel the x, so that the limit is independent of x.
What would f(x) have to be, if f(1/x) is to be proportional to 1/x?
 
  • #3
Would f(x) have to be -x squared if f(1/x) is to be proportional to 1/x
 
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Trigger said:
Would f(x) have to be -x squared if f(1/x) is to be proportional to 1/x

Hint:Relabel 1/x with "lambda",get the old function f(1/x) in terms of "lambda" and then simply rename "lambda" as being x.U'll get your answer.
 

FAQ: Example of Function f:R-R where lim x→0 xf(1/x) ≠ 0

What is a function f:R-R?

A function f:R-R is a mathematical representation that maps each element in the set of real numbers (R) to another element in the same set. It takes an input value (x) and produces an output value (f(x)) based on a specific rule or equation.

What does "lim x→0" mean in the context of a function?

"lim x→0" represents the limit as x approaches 0. In other words, it describes the behavior of a function as the input value (x) gets closer and closer to 0.

Why is it important for xf(1/x) to not equal 0 in this function?

If xf(1/x) were to equal 0, it would mean that the output value (f(x)) is equal to 0 for all inputs close to 0. This would indicate that the function has a horizontal asymptote at x=0, which goes against the requirement that the limit at x=0 must not exist for this function.

Can you provide an example of a function that satisfies lim x→0 xf(1/x) ≠ 0?

One example of such a function is f(x) = sin(1/x). As x approaches 0, sin(1/x) oscillates between -1 and 1, so xf(1/x) will also oscillate and never equal 0.

How can we determine the limit of this function at x=0?

The limit of this function at x=0 can be determined by evaluating the function for different values of x that get closer and closer to 0. If the output values approach a specific number or range of numbers, that would be the limit. However, if the output values do not approach a specific number or range, the limit does not exist.

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