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

In summary, the student is trying to solve for y in terms of dy/dx, but is getting stuck. They simplify the equation and get y=-x-ln2-lnx. Finally, they substitute y back in and get dy/dx=-xy-yln2-ylnx.
  • #1
Nagihiko92
3
0

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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  • #2
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.
 
  • #3
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.
 
  • #4
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.
 
  • #5
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?
 
  • #6
Looks good. Further changes are cosmetic and probably don't matter. Well done.
 

1. What is the derivative of (2/x)^(1/x)?

The derivative of (2/x)^(1/x) is [(1/x)(1- ln(2/x))] * (2/x)^((1/x)-1).

2. How do you simplify (2/x)^(1/x)?

To simplify (2/x)^(1/x), you can rewrite it as e^(ln(2/x) / x), which can be further simplified using the properties of exponents.

3. What is the limit of (2/x)^(1/x) as x approaches infinity?

The limit of (2/x)^(1/x) as x approaches infinity is 1. This can be shown by taking the natural logarithm of the function and using L'Hopital's rule.

4. Can you find the second derivative of (2/x)^(1/x)?

Yes, the second derivative of (2/x)^(1/x) is [(1/x)(1- ln(2/x))] * (2/x)^((1/x)-1) * [(1/x)(1- ln(2/x))] * [(1/x)(1- ln(2/x))-1] - [(1/x^2)(1-ln(2/x))] * (2/x)^((1/x)-1).

5. How can the graph of (2/x)^(1/x) be described?

The graph of (2/x)^(1/x) is a hyperbola that approaches the x-axis and y-axis as x approaches 0. As x approaches infinity, the graph approaches the line y=1.

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