Answer up to a Constant Multiple

Answers up to multiplication

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Complete Code

Download file: AnswerUpToMultiplication.pg

PG problem file

Explanation

DOCUMENT();

loadMacros('PGstandard.pl', 'PGML.pl', 'PGcourse.pl');

Preamble

These standard macros need to be loaded. 
$ans = Compute('(x + 1)(x - 2)')->cmp(
    checker => sub {
        my ($correct, $student, $self) = @_;
        return 0 if $student == 0;
        my $context = Context()->copy;
        $context->flags->set(no_parameters => 0);
        $context->variables->add('C0' => 'Parameter');
        my $c0 = Formula($context, 'C0');
        $student = Formula($context, $student);
        $correct = Formula($context, "$c0 * $correct");
        return $correct == $student;
    }
);

Setup

The answer checker uses a local context with an adaptive parameter to check if the student answer is a parameter C0 multiple of the correct answer. For more on adaptive parameters, see AdaptiveParameters.

BEGIN_PGML
Find a quadratic equation in terms of the variable
[`x`] with roots [`-1`] and [`2`].

[`y =`] [_]{$ans}{15}
END_PGML

Statement

This is the problem statement in PGML. 
BEGIN_PGML_SOLUTION
Solution explanation goes here.
END_PGML_SOLUTION

ENDDOCUMENT();

Solution

A solution should be provided here.