DOCUMENT();
loadMacros(
  "PGstandard.pl",
  "MathObjects.pl",
  "parserMultiAnswer.pl",
  "PGML.pl",
  "PGcourse.pl"
);

################# Setting up the problem goes here.

TEXT(beginproblem());
Context("Numeric");

$m = random(2,6,1);
$b = random(-5,-2,1);

$line = Compute("$m*x+$b")->reduce();

$x1 = random(3,7,1);
$y1 = $line->eval(x=>$x1);

$y2 = random(7,11,1);
$x2 = ($y2-$b)/$m;

$multians = MultiAnswer($line, $y1, $x2)->with(
  singleResult => 0,
  checker => sub {
      my ( $correct, $student, $self ) = @_;
      my ( $linestu, $y1stu, $x2stu ) = @{$student};
      if ($line == $linestu) {
        $result1 = 1;
        $y1calculated = $linestu->eval(x=>$x1);
        if ( $y1calculated == $y1stu ) {
            $result2 = 1;
            } else {
            $result2 = 0;
            }
        $mstu = $linestu->D('x');
        $bstu = $linestu->eval(x=>0);
        $x2calculated = ($y2-$bstu)/($mstu);
        $x2calculated->{tolType}='absolute';
        $x2calculated->{tolerance}=0.5;
        if ($x2calculated == $x2stu) {
            $result3 = 1;
            } else {
            $result3 = 0;
            }
        } else {
        $result1 = 0;
        $result2 = 0;
        $result3 = 0;
        }
        return([$result1,$result2,$result3]);
  });

BEGIN_PGML
Write the equation of [:y= [$line]:].

[:y=:][___________]{$mutians}

When [:x=[$x1]:], predict the value of [:y:].

[:y=:][____]{$multians}

When [:y=[$y2]:], predict the value of [:x:].

[:x=:][____]{$multians}
END_PGML

ENDDOCUMENT();