DOCUMENT();

loadMacros('PGstandard.pl', 'PGML.pl', 'plotly3D.pl', 'PGcourse.pl');


$graph = Graph3D();
$graph->addSurface(
    [ 'x', 'y', 'x^2 + y^2' ],
    [ -3,  3,   30 ],
    [ -3,  3,   30 ],
    variables => [ 'x', 'y' ]
);

BEGIN_PGML
The following is the plot of [`z = x^2 + y^2`]

[@ $graph->Print @]*
END_PGML

BEGIN_PGML_SOLUTION
Solution explanation goes here.
END_PGML_SOLUTION

ENDDOCUMENT();