# [Maxima] confusing solution set of exp-equation

Wolfgang Lindner LindnerW at t-online.de
Mon Apr 16 13:43:00 CDT 2007

```"Stavros Macrakis" <macrakis at alum.mit.edu> schrieb:
On 4/15/07, Wolfgang Lindner <LindnerW at t-online.de> wrote:
>> (%i1) f(x):=exp(x)-1/4*x*exp(x);
>> (%i2) solve(f(x)=0,x);
>> (%o2) [x=4,%e^x=0]
>> (%i3) diff(f(x),x) ;  /* f prime */ ...
>> AFAIK it is not possible to abbrevitae  diff(f(x),x)  with  f'(x).
>> I use fp(x) to name 'f prime' etc.
>> Is there any symbol left (backquote?) to name f'(x) and causing no problems later?
>> What is your recommended work around?

>As a general rule, Maxima does a much better job with mathematical *expressions* than
>with mathematical *functions* with names (like f).
>So the natural way to handle this sort of thing in Maxima is
>f: exp(x)-1/4*x*exp(x);
>solve(f,x)\$
>solve(diff(f,x),x)
> etc.>>

Thank you for your interesting hints on Maxima's capabilities. In Germany we have a
'didactical tradition in math' to perfer *functions* (at least since Felix Klein), not
terms - but using CAS the situation seems be on other one.
My students will (fequently) have to calculate function values, function tables etc.
So - as far as I know - I should have to write

(%i4) subst(x=4, f)  /* instead of f(4) */

if f is an term. Or is there an better possibility?
If there would be an 'term evaluator' like

(%i4') f | x=4         /* term f evaluated for x =4 */

one would have a simpler and shorter 'functionlike' notation.

So I have to decide: function - maybe no good job
term     - no usual evaluation a la f(x)

HTH
Wolfgang
Leichlingen/Germany
```