MathGroup Archive 2011

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Simple question: is it possible to take a derivative and solve for x ?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg119307] Re: Simple question: is it possible to take a derivative and solve for x ?
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Mon, 30 May 2011 06:33:41 -0400 (EDT)

On 5/29/11 at 7:36 AM, t27026t at yahoo.com.br (Alonso) wrote:

>I am a beginner, and would like to know if it is possible to solve
>for x the first derivative of a long equation in Mathematica. Bear
>with me, my background is in Biomedical Sciences.

>I am typing the following command:

>Solve[D[((x*l1 + (1 - x)*l2)/((x^2*v1 + (1 - x)^2*v2 +  2*x*(1 -
>x)*c)^0.5))+((x*L1 + (1 - x)*L2)/((x^2*V1 + (1 - x)^2*V2 +  2*x*(1 -
>x)*C)^0.5)), x]==0,x]

>But Mathematica 8 simply stops, and no output is given.

A portion of the difficulty is likely to be the term

  2*x*(1 - x)*C)^0.5)

  C cannot be used as a variable since it has built-in meaning.
Try changing this to a lower case c and see if that helps. It is
a good idea to avoid using single upper case letters as
variables so as to avoid conflicts with built-in symbols.



  • Prev by Date: Can Mathematica construct a set of equations?
  • Next by Date: Re: Simple question: is it possible to take a derivative and solve for x ?
  • Previous by thread: Simple question: is it possible to take a derivative and solve for x ?
  • Next by thread: Re: Simple question: is it possible to take a derivative and solve for x ?