Finding the Derivative of (2/x)^(1/x)

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Homework Help Overview

The discussion revolves around finding the derivative of the function (2/x)^(1/x) and simplifying the result. The subject area is calculus, specifically focusing on differentiation techniques and logarithmic properties.

Discussion Character

  • Mathematical reasoning, Problem interpretation, Assumption checking

Approaches and Questions Raised

  • Participants explore the use of logarithmic differentiation and implicit differentiation to find the derivative. There are questions about whether to use the exponential function to isolate y or to differentiate directly. Some participants express uncertainty about the presence of y in the final derivative and discuss simplification steps.

Discussion Status

The discussion is active, with participants identifying mistakes in their differentiation process and correcting them. There is a focus on ensuring that the final expression does not contain the variable y, and some guidance has been provided regarding the simplification of the derivative.

Contextual Notes

Participants mention a minor typo in the initial setup and discuss the implications of their differentiation steps, indicating a learning process around the rules of differentiation and logarithmic identities.

Nagihiko92
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Homework Statement


Find (2/x)^(1/x). Simplify your answer.


Homework Equations





The Attempt at a Solution


I let y = (2/x)^(1/x)
lny = ln(2/x)^(1/x)
lny= ln(2/x)/x
However, I get stuck here and don't know whether I should use e on both sides to get y by itself or to use implicit differentiation to get dy/dx directly.
 
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Nagihiko92 said:
I let y = (2/x)^(1/x)
lny = ln(2/x)^(1/x)
lny= ln(2/x)/x
However, I get stuck here and don't know whether I should use e on both sides to get y by itself or to use implicit differentiation to get dy/dx directly.
Minor typo... there's a missing bracket in the second line, but the third line is correct so that's okay.

If you use e on both sides you just get back what you started with. So that's no good. Try the other. Not sure what you mean by "implicit differentiation". Just differentiate both sides by x.
 
Ok so by using implicit differentiation and simplifying ln(2/x) as ln2 - lnx, I get
(1/y)(dy/dx) = ((x)(0-1/x) - (ln2-lnx)(1))/x
(1/y)(dy/dx) = (-x - ln2 - lnx)/x²
dy/dx = y(-x - ln2 - lnx)/x²

And my final answer turns out
dy/dx = (-xy - yln2 - ylnx)/x²

Did I do something wrong? It looks like I made it even more confusing.
 
Nagihiko92 said:
Ok so by using implicit differentiation and simplifying ln(2/x) as ln2 - lnx, I get
(1/y)(dy/dx) = ((x)(0-1/x) - (ln2-lnx)(1))/x
(1/y)(dy/dx) = (-x - ln2 - lnx)/x²
dy/dx = y(-x - ln2 - lnx)/x²

And my final answer turns out
dy/dx = (-xy - yln2 - ylnx)/x²

Did I do something wrong? It looks like I made it even more confusing.

You can't have y in your answer. That was a variable you introduced. There is also an error in your differentiation of a quotient, and another error later on in the simplifications. But you are on the right track.
 
Ok, so I found my mistakes

(1/y)(dy/dx) = ((x)(-1/x) - (ln(2/x))(1))/x²
(1/y)(dy/dx) = (-1 - ln2 + lnx)/x²
dy/dx = y(-1 - ln2 + lnx)/x²

And if I can't leave y in my answer, I substituted y back in as

dy/dx = ((2/x)^(1/x)(-1 - ln2 + lnx))/x²
Should I factor in the (2/x)^(1/x) or leave it like that?
 
Looks good. Further changes are cosmetic and probably don't matter. Well done.
 

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