## WeBWorK Problems

### Simplifying Derivatives

by Danny Glin -
Number of replies: 3
Looking at the following code (for example):

Context("Numeric");
$f=Formula("2x^3");$g=$f->D(x)->reduce; This gives a formula for$g of the form "2*3x^2".
Is there a way to get webwork to simplify this answer (i.e. multiply the two constants together)?
In reply to Danny Glin

### Re: Simplifying Derivatives

by Davide Cervone -
The reduction rules are really very simple-minded, and are not a full Computer Algebra System. There is a lot more that could be done with them, but in their current form, the reduction you ask for is not available. Sorry!

Davide
In reply to Davide Cervone

### Re: Simplifying Derivatives

by Dick Lane -
If I ask a student to differentiate a function and analyze that derivative function, I would like feedback (after closing date) about the first step to be close to a student's unsimplified result.  E.g., for
$p = Formula( "$a ($b x -$c) ($d x -$e)" ) ;
$p1 =$p -> D(x) ;
I would be content if the student saw $p1 displayed as$a * $b ($d x - $c) +$a ($b x -$c) $d involving just the Product Rule (and simpler stuff). On the other hand, if I also asked for identification of critical point(s), then my Solution would include suitable algebra (with simplification of that derivative expression which keeps$a as a factor for other stuff).

I have had my calculus students use a CAS for many (20+) years and I often wish Webwork had a CAS.  The several Student packages in Maple (and rewrite rules in Derive & MuMath) show there is pedagogical value in selective inhibiting the power of a CAS.  I am not upset with MathObject symbolic reduction rules being simple-minded.
In reply to Dick Lane

### Re: Simplifying Derivatives

by Paul Pearson -
Dear Dick,

You can require student answers to be factored:

http://webwork.maa.org/wiki/FactoringAndExpanding

Also, you should be able to use AnswerHints.pl to provide feedback comments to students who have a correct answer that is not fully factored:

http://webwork.maa.org/wiki/AnswerHints

Good luck!

Paul