I suspect this may have to do with your formula for $f.  Try this

$x01=-$x0;
$f=$a1/$a2*($x01+x)+$y0;

This may potentially be a bug.  The best action would be to send the worksheet to support@maplesoft.com.  This action would allow us to replicate the problem and determine if the root cause is with the Mathapp or Maple T. A. specific.  

Hello Stéphane,

What example are you using that shows the tutors, etc?

Robin

Technical Support Analyst

1-800-267-6583 x413

support@maplesoft.com

www.maplesoft.com/support