## DESCRIPTION
## Conic Sections
## ENDDESCRIPTION

## KEYWORDS('calculus','conic section','parabola','focus','directrix')
## Tagged by cmd6a 5/30/06

## DBsubject('Calculus')
## DBchapter('Parametric Equations and Polar Coordinates')
## DBsection('Conic Sections')
## Date('1/12/2000')
## Author('Zig Fiedorowicz')
## Institution('Rochester')
## TitleText1('Calculus: Early Transcendentals')
## EditionText1('5')
## AuthorText1('Stewart')
## Section1('C')
## Problem1('')

## TitleText2('Calculus: Early Transcendentals')
## EditionText2('6')
## AuthorText2('Stewart')
## Section2('C')
## Problem2('')

DOCUMENT();        # This should be the first executable line in the problem.

loadMacros(
"PG.pl",
"PGbasicmacros.pl",
"PGchoicemacros.pl",
"PGanswermacros.pl",
"PGauxiliaryFunctions.pl"
);

$showPartialCorrectAnswers = 1;
if (!($studentName =~ /PRACTICE/)) {
$seed = random(1,4,1);
if ($studentName =~ /VINCE VERSION1/) {$seed = 1;}
if ($studentName =~ /VINCE VERSION2/) {$seed = 2;}
if ($studentName =~ /VINCE VERSION3/) {$seed = 3;}
if ($studentName =~ /VINCE VERSION4/) {$seed = 4;}
SRAND($seed);}

$a = random(2,10,1);
$b = random(3,11,1);
if ($a==$b) {$b++;}
$m = 2*($a+$b);
$c = ($b-$a)/2;
$ans = "$c - y^2/$m";

TEXT(&beginproblem);
BEGIN_TEXT
Find an equation of the parabola with focus at \((- $a,0)\) and with directrix
\(x = $b\). Express your answer in the form \(x = f(y)\).
$BR
Answer: \(x=\) \{ans_rule(40)\}

END_TEXT

&ANS(function_cmp($ans,"y"));


ENDDOCUMENT();