JavaScript Tutorial - Quadratic

Tutorial - Quadratic Formula

In mathematics, a quadratic equation is a polynomial equation of the second degree. The general form is

where x represents a variable, and a, b, and c, constants, with a ≠ 0. (If a = 0, the equation becomes a linear equation.)

The constants a, b, and c, are called respectively, the quadratic coefficient, the linear coefficient and the constant term or free term. The term "quadratic" comes from quadratus, which is the Latin word for "square". Quadratic equations can be solved by factoring, completing the square, graphing, Newton's method, and using the quadratic formula.

The roots are given by the quadratic formula:

Output of this tutorial will be display as the following:

Source Code in JavaScript of Quadratic Equation:

<script>
document.write("<h1>Quadratic Equation</h1>"); //Display the title

do
{
 var a = prompt("Enter cofficient a (a not equal to 0):");
}while(a==0) //User will be allow to continue when key in value for a coefficient that is non-zero in quadratic equation

do
{
var b = prompt("Enter cofficient b :"); //User provide b coefficient in quadratic equation
var c = prompt("Enter cofficient c :"); //User provide c coefficient in quadratic equation
}while(Math.pow(b,2)<(4*a*c))  //b^2 - 4ac must greater and equal than zero as we cant square root a negative number.

var eq="";  //set the equation to null string

if(Math.abs(a)==1) //Check if a coefficient is equal to one
 eq = (a<0?"-":"")+"x²"; //Display X^2 or -X^2 depend on sign in front of one for a coefficient
else
 eq = a+"x²"; //Display aX^2 where a coefficient rather than 1 or -1

if(b!=0) //Check b is not null
{
 if(Math.abs(b)==1)
  eq+=(b<0?"-":"+")+"x"; //Display X or -X depend on sign in front of one for b coefficient
 else
  eq+=(b>0?"+"+b:b)+"x"; //Display bX where b coefficient rather than 1 or -1
}

if(c!=0)
 eq+=(c>0?"+"+c:c); //Display + or - depend or c coefficient

var x1 = ((-1*b)+Math.sqrt(Math.pow(b,2)-(4*a*c)))/(2*a); //Calculate X1
var x2 = ((-1*b)-Math.sqrt(Math.pow(b,2)-(4*a*c)))/(2*a); //Calculate X2

document.write("<h2>Expression : </h2>");
document.write("<p style='text-indent:15px; font-size:14pt'>"+eq+"</p>"); // Display the final equation

document.write("<b><i>where,</i></b><br />");
document.write("<i>a="+a+"; b="+b+"; c="+c+"</i>"); //Show the a, b and c coefficient
document.write("<h2>Solution to X : </h2>");
document.write("<p style='text-indent:15px; font-size:14pt'>x₁="+x1.toFixed(2)+"</p>"); //Display X1 value
document.write("<p style='text-indent:15px; font-size:14pt'>x₂="+x2.toFixed(2)+"</p>");
//Display X2 value
</script>