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TomLikesPhysics
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I can only find derivative for x>0 , but I don't know why (according to wolfram).
 one year ago
 one year ago
TomLikesPhysics Group Title
I can only find derivative for x>0 , but I don't know why (according to wolfram).
 one year ago
 one year ago

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TomLikesPhysics Group TitleBest ResponseYou've already chosen the best response.0
mom I need to attach the equations
 one year ago

TomLikesPhysics Group TitleBest ResponseYou've already chosen the best response.0
My f`is apparently only true for x>0 and I have no clue where I make that assumption in my differentiation.
 one year ago

Zekarias Group TitleBest ResponseYou've already chosen the best response.0
Your f' is defined only for R\{6^{0.5), 6^(0.5)}, actually
 one year ago

TuringTest Group TitleBest ResponseYou've already chosen the best response.0
how do you figure @Zekarias
 one year ago

TuringTest Group TitleBest ResponseYou've already chosen the best response.0
f' is not defined at +/6^(0.5), but it is for all other points as far as I see
 one year ago

TuringTest Group TitleBest ResponseYou've already chosen the best response.0
I do see one problem which is that for 6^(0.5)<x0 the slope should be negative, but the derivative is positive
 one year ago

TuringTest Group TitleBest ResponseYou've already chosen the best response.0
6^(0.5)<x<0 I meant
 one year ago

TuringTest Group TitleBest ResponseYou've already chosen the best response.0
http://www.wolframalpha.com/input/?i=plot%20y%3D(x%5E26)%5E(2%2F3)&t=crmtb01 you can see the slope is negative for 6^(1/2)<x<0, but the derivative would be positive as you have it
 one year ago

TomLikesPhysics Group TitleBest ResponseYou've already chosen the best response.0
ok, so how should I take the derivative then? Without rewriting it and using the chainrule over and over?
 one year ago

TuringTest Group TitleBest ResponseYou've already chosen the best response.0
that I'm not so sure about. I'm thinking on it.
 one year ago

TuringTest Group TitleBest ResponseYou've already chosen the best response.0
@amistre64 any ideas here?
 one year ago

amistre64 Group TitleBest ResponseYou've already chosen the best response.2
the derivative on the attachment looks fine; im not sure what the question is tho
 one year ago

TuringTest Group TitleBest ResponseYou've already chosen the best response.0
http://www.wolframalpha.com/input/?i=derivative+of+y%3D%28x%5E26%29%5E%282%2F3%29 true I don't see wolf giving the condition that x>0
 one year ago

TuringTest Group TitleBest ResponseYou've already chosen the best response.0
but what about the point I brought up? f' for 6^(1/2)<x<0 should be negative, but it's positive
 one year ago

amistre64 Group TitleBest ResponseYou've already chosen the best response.2
http://www.wolframalpha.com/input/?i=derivative+cbrt%28%28x%5E26%29%5E2%29 i think this has more intricate workings than we think
 one year ago

amistre64 Group TitleBest ResponseYou've already chosen the best response.2
\[u=(x^26)^2~:~u'=4x(x^26)\] \[D[u^{1/3}]=\frac{u^{1/3}}{3}u'\] \[D[u^{1/3}]=\frac{4x(x^26)}{3((x^26)^2)^{1/3}}\]
 one year ago

amistre64 Group TitleBest ResponseYou've already chosen the best response.2
at 1\[\frac{*}{+}=+\]
 one year ago

TuringTest Group TitleBest ResponseYou've already chosen the best response.0
but that should not be if you look at the graph http://www.wolframalpha.com/input/?i=plot%20y%3D(x%5E26)%5E(2%2F3)&t=crmtb01 should be f'<0 at x=1
 one year ago

amistre64 Group TitleBest ResponseYou've already chosen the best response.2
notice that the function\[\sqrt[3]{((x^26)^2)}\ne \left(\sqrt[3]{(x^26)}\right)^2\]at all points http://www.wolframalpha.com/input/?i=%28%28x%5E26%29%5E2%29%5E%281%2F3%29++%28%28x%5E26%29%5E%281%2F3%29%29%5E2
 one year ago

amistre64 Group TitleBest ResponseYou've already chosen the best response.2
the subtlties are in how we are not using the "correct" use of a derivative
 one year ago

amistre64 Group TitleBest ResponseYou've already chosen the best response.2
the way we are used to working with exponents seems to be a misuse of notation and doesnt express the full nature of the problem http://www.wolframalpha.com/input/?i=y%3D%28%28x%5E26%29%5E2%29%5E%281%2F3%29%2C+y%3D+%28%28x%5E26%29%5E%281%2F3%29%29%5E2
 one year ago

TomLikesPhysics Group TitleBest ResponseYou've already chosen the best response.0
So I should not rewrite the equation and just use the chainrule multiple times then to end up with the same answer as wolfram does?
 one year ago

amistre64 Group TitleBest ResponseYou've already chosen the best response.2
correct, I would simplify it by making a substitution; then replacing those values in the end
 one year ago

TomLikesPhysics Group TitleBest ResponseYou've already chosen the best response.0
k, thx. I will try that now.
 one year ago

TomLikesPhysics Group TitleBest ResponseYou've already chosen the best response.0
Damn. That went well and it was pretty quick and easy too. So the first attempt did not work because I messed the exponents up?
 one year ago
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