<?php        // Gemaakt op PHP versie 4.3.4

echo '<br><br>Gebruik bij decimalen een punt, dus geen komma!<br><br>';

if($_GET['submit'])
{ 
	//Kijkt of er iets is ingevuld
	$minb = - $_GET['b']; //-b
	$tweea = 2 * $_GET['a']; // 2a
	$D = pow($_GET['b'], 2) - (4 * $_GET['a'] * $_GET['c']); //D = b^2 - 4ac
	$D2 = pow($D, 0.5) / $tweea; // "wortel"-D / 2a (tot de halve macht = wortel)
	$xtop = $minb / $tweea; // -b / 2a (=Xtop)
	$x1 = $xtop - $D2; // -b/2a - wrtl-D/2a
	$x2 = $xtop + $D2; // -b/2a + wrtl-D/2a

	$ytop = $_GET['a'] * pow($xtop, 2) + $_GET['b'] * $xtop + $_GET['c'] //Xtop invullen
	or $_GET['a'] * pow($xtop, 2) - $_GET['b'] * $xtop - $_GET['c'];
	
	if ($D >= 0)
	{  //Alleen weergeven als D positief is
		echo '<b>Discriminant:</b> ' . $D . '<br>'; //echo Discriminant
		echo '<b>X<sub>1</sub>:</b> ' . $x1 . '<br>'; //echo Eerste nulpunt
		echo '<b>X<sub>2</sub>:</b> ' . $x2 . '<br>'; //echo Tweede nulpunt
		echo '<b>X<sub>top</sub>:</b> ' . $xtop . '<br>'; //echo Xtop
		echo '<b>Y<sub>top</sub>:</b> ' . $ytop . '<br><br>'; //echo Ytop
	}
	
	else
	{
		echo '<b>Discriminant is negatief : ' . $D . '<br><br>
		<form method="GET" action="index.php?page=abc" name="abcformule">
		<input type="hidden" name="page" value="abc">
		<b>a = <input type="text" name="a"><br>
		b = <input type="text" name="b"><br>
		c = <input type="text" name="c"><br>
		<input type="submit" name="submit" value="Bereken">
		<input type="reset" name="reset" value="Reset">'; //Als discriminant negatief is
	}
}

else
{ //Als er nog niets is ingevuld
	echo '<form method="GET" action="index.php?page=abc" name="abcformule">
	<input type="hidden" name="page" value="abc">
	<b>a = <input type="text" name="a"><br>
	b = <input type="text" name="b"><br>
	c = <input type="text" name="c"><br>
	<input type="submit" name="submit" value="Bereken">
	<input type="reset" name="reset" value="Reset">';
}
?> 