FormulasUpToMultiplication

Formulas Up To Multiplication by a Nonzero Constant

This PG code shows how to check student answers that are correct up to multiplication by a nonzero constant.

Problem Techniques Index

PG problem file	Explanation
DOCUMENT(); loadMacros( "PGstandard.pl", "MathObjects.pl", ); TEXT(beginproblem());	Initialization: We need only essential macros.
Context("Numeric"); $aSolution = Compute("(x-2)(x+1)");	Setup: Nothing surprising here.
BEGIN_TEXT Find a quadratic equation in terms of the variable \( x \) with roots \( -1 \) and \( 2 \). $PAR y = \{ ans_rule(30) \} END_TEXT	Main Text: The problem text section of the file is as we'd expect.
$showPartialCorrectAnswers = 1; ANS( $aSolution->cmp(checker => sub { my ( $correct, $student, $self ) = @_; my $context = Context()->copy; return 0 if $student == 0; $context->flags->set(no_parameters=>0); $context->variables->add('C0'=>'Parameter'); my $c0 = Formula($context,'C0'); $student = Formula($context,$student); $correct = Formula($context,"$c0 * $aSolution"); return $correct == $student; } ) ); ENDDOCUMENT();	Answer Evaluation: We use a local context with an adaptive parameter to check the answer. For more on adaptive parameters, see AdaptiveParameters When $aSolution is "complicated", you may need to replace $c0 * $aSolution in the custom answer checker by its value $c0 * (x-2)(x+1) in order to get things to work correctly.

Problem Techniques Index