eq:''diff(x + y =a, x);solve([eq],[dy/dx]);



Exactly Albert.

But this is not work in:

diff(ev(y, solve(x^.5+y^.5=a^.5, y)), x);

Maxima ask me:

Is  SQRT(a) - SQRT(x)  positive, negative, or zero?

How I say it to maxima?
How I say to maxima that a>=0 and  0<=x<=a and 0<=y<=a?
[]´s

Em Sat 23 Apr 2005 14:17, Albert Reiner escreveu:
> [Jorge Barros de Abreu , Sat, 23 Apr 2005 13:57:02 
-0300]:
> > Hi for all.
> > How I make the following situation?
> >
> > depends(y,x);
> > eq:''diff(x + y =a, x);
>
> This differentiates both sides of the equation with respect to x.  The
> result is the equation 1 = 0.
>
> > solve([eq01],[dy/dx]);
>
> I suspect you want something like
>
> diff(ev(y, solve(x+y=a, y)), x); ==> -1 //
>
> HTH,
>
> Albert.
>
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