Is the Antiderivative of 2(1 + ln(x))(x^x)^2 Solvable?

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Discussion Overview

The discussion revolves around the antiderivative of the expression 2(1 + ln(x))(x^x)^2. Participants explore methods for integration, share their approaches, and reflect on the problem's complexity.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant claims that the expression is not algebraically solvable as it stands.
  • Another suggests using substitution with u = (x^x)^2, which is met with positive acknowledgment.
  • A different participant asserts that the antiderivative simplifies to x^(2x).
  • Further elaboration on the substitution method is provided, detailing the differentiation process and resulting integral.
  • Some participants discuss the reasoning behind the substitution choice, linking it to the presence of logarithmic terms in the derivative of x^x.
  • One participant humorously speculates on the nature of the solution's discovery, suggesting it might involve divine intervention or a deal with a demon.
  • Another participant reflects on their thought process in arriving at the substitution, indicating prior knowledge of the answer may have influenced their approach.
  • Corrections are made regarding the inclusion of dx in the integral and the possibility of using u = x^x as an alternative substitution.
  • A participant shares their detailed working through the substitution method, arriving at the same conclusion as others, though they express uncertainty about its correctness.
  • Concerns about clarity in mathematical notation are raised, with a suggestion for using LaTeX for better understanding.
  • One participant notes that the original problem seemed unsolvable due to a potential misinterpretation of the expression's formatting.

Areas of Agreement / Disagreement

While some participants agree on the substitution method leading to the same antiderivative, there remains uncertainty regarding the clarity and correctness of the initial problem statement and its formatting. The discussion does not reach a consensus on the overall solvability of the original expression.

Contextual Notes

Participants express varying levels of confidence in their methods and solutions, with some noting the potential for misinterpretation of the problem's structure affecting their approaches.

roam
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[SOLVED] Unsolvable Problem?

Hello!

How can we find the antiderivative of [tex]2(1 + lnx)(x^x)^2[/tex]


As it stands it is not algebraically solvable.
This question is from my calculus' book, but the solutions are not provided...

Does anyone know of any mthod we can use to integrate this?

:confused:
 
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Substitution. [tex]u=(x^x)^2[/tex].
 
Oh, that is clever!
 
actually that is the antiderivative x^(2x)
 
Yep.

[tex]\int 2(1+\log x)(x^x)^2\, dx[/tex]: [tex]u=(x^x)^2[/tex]; by logarithmic differentiation we find [tex]du=2(x^x)^2(\log x + 1)[/tex] so the integral is [tex]\int\, du = u = (x^x)^2 = x^{2x}[/tex].
 
so how did you figure out that substitution?
 
If I had to guess, I'd have to say it was either
1. a barter for his soul with some demon/deity
2. divine intervention
3. ? can't think of any other possibility

Seriously, that was clever
 
I suspect that he realized that, since the derivative of xx involves a logarithm, and there was a logarithm in the problem, he should try something like u= xx, tried it, saw that it didn't quite work and then played with it until he found something that did.

Two many math students seem to think that the way you solve a math problem is to stare at the paper until the solution springs, like Venus, full grown from your forehead.
 
HallsofIvy said:
I suspect that he realized that, since the derivative of xx involves a logarithm, and there was a logarithm in the problem, he should try something like u= xx, tried it, saw that it didn't quite work and then played with it until he found something that did.

Two many math students seem to think that the way you solve a math problem is to stare at the paper until the solution springs, like Venus, full grown from your forehead.

maybe but writing simply for the sake of writing isn't effective either.
 
  • #10
I dunno, I just saw it and tried it and voilà, it worked.

I knew the answer was [tex](x^x)^2[/tex] before I solved the problem, which may or may not have helped, but probably did.
 
  • #11
Also I left out a [tex]dx[/tex] in my first post.
 
  • #12
Also (and sorry for the triple post!) [tex]u=x^x[/tex] would have worked just as well.
 
  • #13
O.K...

Here is my working, by using substitution:


Let I = ∫2(1+lnx)(x^x)2 dx

Let u = x^x

∴ lnu = lnx^x

∴ lnu = xlnx

∴ 1/u × dudx = x×1/x + 1×lnx

∴ du/dx = u ×(1+lnx)

∴ du = x^x^×(1+lnx)dx

∴ dx = du / x^x^×(1+lnx)

∴ I = ∫2(1+lnx)(x^x)^2 dx

= ∫2(1+lnx)(x^x)^2{du / [x^x×(1+lnx)]}

= ∫2 x^xdu

= ∫ 2u du

= u² + c

= (x^x)^2 + c

= x^2x + c


I didn't know if it was correct but now since you have the same solution as me then it must be right...

Many thanks.
 
Last edited:
  • #14
Yep, that seems right although it was hard to follow somewhat because you didn't use LaTeX...
 
  • #15
That makes for quite an amusing thread title! :-p
 
  • #16
I concur.
 
  • #17
Oh man I was just thinking that! You have mah brain, cristo.
 
  • #18
my calculus teacher taught us this a couple weeks ago. its pretty useful
 
  • #19
Sorry...

I know...about the title... :blushing: :redface:

But it looked unsolvable to me because the original question looked like this: [tex]2(1 + lnx)x^{x^2}[/tex]

I reckon they forgot to include the brackets. But my teacher then told me to include the brackets and then solve it that way.
[tex]2(1 + lnx)(x^x)^2[/tex]

Thanks.
 

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