<?php //by scrat if(!isset($_POST['go'])) { echo "<form action=par.php method=post> y=<input type=text name=a value=a>*x^2+ <input type=text name=b value=b>*x+<input type=text name=c value=c><br> <input type=submit name=go value=Draw>"; } else { $im=imagecreate(640,480); header("Content-type: image/png"); imagecolorallocate($im,255,255,255); $black=imagecolorallocate($im,0,0,0); $red=imagecolorallocate($im,255,0,0); imageline($im,320,0,320,480,$black); imageline($im,0,240,640,240,$black); for($i=0;$i<640;$i+=0.01) { $i>320 ? $k=$i-320 : $k=320-$i; $y=((-$_POST['a'])*($k*$k)+$_POST['b']*$k+$_POST['c'])+240; imagesetpixel($im,$i,$y,$red); } imagepng($im); } ?>