<html>
<head>
<script type="text/javascript">
function main(){
/*--------------------------------------------*/
var eA=document.getElementById('a').value;
var eB=document.getElementById('b').value;
var eC=document.getElementById('c').value;
var eD=document.getElementById('verso').value;
/*--------------------------------------------*/
var a=parseFloat(a);
var b=parseFloat(b);
var c=parseFloat(c);
var s=parseInt(verso);
/*--------------------------------------------*/
if(a<0){
if(s>2){
if(s==3){
s=1;
}
else{
s=2;
}
}else{
if(s==1){
s=3;
}
else{
s=4;
}
}
a=a*-1;
b=b*-1;
c=c*-1;
}
}
/*--------------------------------------------*/
var delta=[(eB*eB)-4*(eA*eC)];
if(delta==0){
zero();
}
else{
if(delta>=1){
posit();
}
else{
negav();
}
}
/*--------------------------------------------*/
function negav(){
if(s>2){
document.write('∃x');
}
else{
document.write('∀x');
}
}
/*--------------------------------------------*/
function zero(){
if(s>2){
if(s==3){
document.write('∃x∈R');
}
else{
document.write('Soluzioni coincidenti');
}
}
}
/*--------------------------------------------*/
function posit(){
var d1=Math.sqrt(delta);
var x1=(-eB +d1)/(2*eA);
var x2 = (-eB-d1)/(2*eA);
if(s>2){
if(s==3){
document.write(x1<'x'<x2);
}
else{
document.write(x1'≤x≤'x2);
}
}
else{
if(s==1){
document.write('x<'x1'∨x'>x2);
}
else{
document.write('x≤'x1'∨x≥'x2);
}
}
}
</script>
<title>Disequazioni di II grado</title>
<style type="text/css">
.form {background: blue; color:#FFFFFF; font-family: Tahoma; font-size: 14px; border: Solid 2px #000000;}
</style>
</head>
<body>
<h3>Disequazione di 2º</h3
<form id="fomr1" method="post">
<input type="text" id="a" value="Inserisci a" tabindex="1" class="form" />
⋅x² +
<input type="text" id="b" value="Inserisci b" tabindex="2" class="form" />
⋅x +
<input type="text" id="c" value="Inserisci c" tabindex="3" class="form" />
<select id="verso" tabindex="4">
<option value="1"selected="selected">></option>
<option value="2">≥</option>
<option value="3"><</option>
<option value="4">≤</option>
</select>
<input type="button" id="risolvi" value="risolvi" onclick="main()"/>
</form>
</body>
</html>