Roots of Quadratic Equation: JavaScript

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Quadratic Equations are of the form ax2 + bx + c = 0. To find roots(root1 and root2) of such an equation, we need to use the formula

quadratic equation Roots of Quadratic Equation: JavaScript


Video Explaining The JavaScript Code To Find Roots of a Quadratic Equation:


YouTube Link: http://www.youtube.com/watch?v=Td6QViKdbZU [Watch the Video In Full Screen.]




To calculate the roots of a quadratic equation using a computer program, we need to break down the formula and calculate smaller parts of it and then combine to get the actual solution.

So lets calculate square root of b2 – 4 * a * c and store it in variable root_part. Also store 2 * a in variable denom. Now calculate ( – b + root_part ) / denom and store it in root1 and ( – b – root_part ) / denom in root2.
Output the values of root1 and root2 to the browser using document.write statement.

Javascript Coding Explained In Above Video:

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<html>
 <head><title>Quadratic Equation</title></head>
 <body>
 
	<script type="text/javascript">
	<!--
		var a = prompt("Enter value of a","1");
		var b = prompt("Enter value of b","4");
		var c = prompt("Enter value of c","4");
 
		var root_part = Math.sqrt(b * b - 4 * a * c);
		var denom = 2 * a;
 
		var root1 = ( -b + root_part ) / denom;
		var root2 = ( -b - root_part ) / denom;
 
		document.write("1st root: "+root1+"<br />");
		document.write("2nd root: "+root2+"<br />");
 
	// -->
	</script>
 
 </body>
</html>

Usually people will make mistake in this line

var root_part = Math.sqrt(b * b - 4 * a * c);

Be sure that, you write capital letter M in Math.sqrt.

Work Space:
Quadratic Equation: ax2 + bx + c = 0
Let,
a = 1
b = 4
c = 4
i.e., 1x2 + 4x + 4 =0
=> 1x2 + 2x + 2x + 4 = 0
=> x ( x + 2 ) + 2 ( x + 2 ) = 0
=> ( x + 2 ) + ( x + 2 ) = 0
=> x + 2 = 0 AND x + 2 = 0
=> x = -2 AND x = -2


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