DOCUMENT();loadMacros("PG.pl","PGbasicmacros.pl","PGchoicemacros.pl","PGanswermacros.pl","PGauxiliaryFunctions.pl","MathObjects.pl","parserFormulaUpToConstant.pl",);Context("Numeric")->flags->set(formatStudentAnswer => parsed,reduceConstants => 0,reduceConstantFunctions => 0,);Parser::Number::NoDecimals;$fx = Formula("3 x sqrt(x - 8)");$fx->{limits} = [9,10];$ans = FormulaUpToConstant("6/5*(x-8)^(5/2) + 16*(x-8)^(3/2)");$ans->{limits} = [9,10];#########################################TEXT(beginproblem());$showPartialCorrectAnswers = 1;Context()->texStrings;BEGIN_TEXT$PAREvaluate the indefinite integral:$PAR\( \displaystyle \quad\quad \int $fx \, dx = \)\{ ans_rule(40) \}END_TEXTContext()->normalStrings;#########################################ANS( $ans -> cmp(showHints => 1) -> withPostFilter(sub {my $ans = shift;$ans->{ans_message} = "" if $ans->{ans_message} eq"This answer is equivalent to the one you just submitted.";return $ans;}));ENDDOCUMENT();

If I submit an answer like 6/5*(x-8)^(5/2) + 16*(x-8)^(3/2) without adding a constant C, I cannot get the helpful hint message: Your answer is not the most general solution. This is different from other anti-derivative problems, for example, if I change this line:

$ans = FormulaUpToConstant("6/5*(x-8)^(5/2) + 16*(x-8)^(3/2)");

to

$ans = FormulaUpToConstant("x");

and submit an answer x, I will get a hint: Your answer is not the most general solution. Can anyone give me some help about how to fix this problem?

As a side note, I tried to fix it by adding some scripts like:

ANS( $ans->cmp() -> withPostFilter(sub {my $ans = shift;if(($ans->{score} == 0) && (!($ans->{ans_message}))){$stuAns = $ans->{original_student_ans};$stuAns =~ s/(sqrt)/::/g;$stuAns =~ s/([a-zA-Z]+)/x/g;$stuAns =~ s/::/sqrt/g;$stuAns = Formula("$stuAns")->D();$ans->{ans_message} = "Your answer is not the most general solution." if ($fx == $stuAns);}$ans->{ans_message} = "" if $ans->{ans_message} eq"This answer is equivalent to the one you just submitted.";return $ans;}));

but it gives me some other troubles. For example, if I submit an answer like 6/5*(8-x)^(5/2) + 16*(8-x)^(3/2)+C, I will get an warning because of this line:

$ans->{ans_message} = "Your answer is not the most general solution." if ($fx == $stuAns);

Any insight on what could be going on would be really appreciated.

Thanks,

Liping