** Using WeBWorK **

Hi Alberto,

Thanks for reporting the bug. It is now fixed in the svn. I had difficulty locating the pg problem which is NationalProblemLibrary/ASU-topics/setDerivativeBasicFunctions/3-7-13.pg. You seem to have a different name/location for the problem. For future reference when reporting bugs in problems it is best to first go to "Edit this problem" and then click on "report problem bugs". This gives more information about the bug, e.g. the seed and precise name of the problem.

The bug in the problem is a typical error. In my example the correct answer is 230x - (x**2)/70.

By default WeBWorK uses test values in the range (0,1) and basically checks if the student's answer and the correct answer agree up to .1 percent. For test points in this range, 230x - (x**2)/70 and 230x - (2x)/70 are closer than that. To fix this you can adjust the tolerance or the range the test valuse take. I did the later changing

$ans = "$c*x - (x**2)/$a";
ANS(fun_cmp($ans));

to

$ans = "$c*x - (x**2)/$a";
ANS(fun_cmp($ans, limits=>[-100,100]));

Arnie