Find the appropriate delta for f(x)=1/x - 0.5

In summary, the conversation discusses finding a number delta for the equation |1/x - 0.5| < 0.2 whenever |x - 2| < delta. The suggested approach involves factoring out a negative exponent and finding a delta that satisfies the equation.
  • #1
xviddivxoggmp3
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Homework Statement



find a number delta

Homework Equations



f(x) = 1/x

| 1/x - 0.5 |<0.2 whenever | x - 2 | < delta

The Attempt at a Solution



how would you factor out a negative exponent?
is this possible?
i think i can get x out from under the 1/x with using negative exponents, but how would i factor it out? is this the wrong way to go with this?

|1/x - 1/2| < 0.2
| x - 2|^-1 < 0.2
 
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  • #2
your equation is wrong as you suspected...

[tex]|1/x-1/2|\neq |x-2|^{-1}[/tex]

I suggest this first approach:

[tex]|1/x-1/2|=|(2-x)/2x|=|1/2x||x-2|[/tex]

So that now finding delta such that |x-2|<delta ==> |1/x-1/2|<0.2 is equivalent to finding delta such that |x-2|<delta ==> |x-2|<|2x|0.2=0.4|x|

This reads "As soon as the distance from x to 2 is smaller than 0.4 times the distance from x to 0, then we have |1/x-1/2|<0.2".

Pick your favorite delta satisfying this.
 

1. What is the definition of ε and δ in this context?

In this context, ε represents the desired margin of error or maximum distance between the actual value of f(x) and the limit L. δ represents the corresponding maximum distance between the input x and the limit point c.

2. How do you find ε and δ for a given function?

To find ε and δ for a given function, we follow the definition of a limit and use algebraic manipulation to isolate δ in terms of ε. This typically involves setting an inequality using the definition of a limit and solving for δ by manipulating the expression.

3. What is the purpose of finding ε and δ for a function?

The purpose of finding ε and δ for a function is to determine the behavior of the function near a specific point, also known as the limit point. It allows us to quantify how close the function is to approaching a certain value, and helps us understand the continuity and differentiability of the function at that point.

4. Can ε and δ be any value?

No, ε and δ must satisfy certain conditions for the limit to exist. Specifically, ε must be positive and δ must be positive and can vary based on ε. Additionally, the value of δ must ensure that the output of the function falls within the range of ε from the limit point.

5. Are there any limitations to finding ε and δ for a function?

Yes, finding ε and δ can be a challenging process and may not be possible for all functions. In some cases, it may be necessary to use advanced techniques such as the squeeze theorem or L'Hopital's rule to find ε and δ. Additionally, the behavior of a function near a certain point may be complex and may not be accurately captured by a single value of ε and δ.

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