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Realize the effect of univariate quadratic equation through JS. Enter the coefficients of a, B and C to calculate the values of X1 and x2

2022-07-29 04:16:00 【Xiao Yang should work hard】

Catalog

        First step ： frame

        The second step ： We know , The expression of univariate quadratic equation is ​ edit

                 The root formula is  

      The third step ： We define three variables to receive a,b,c

      Step four ： Next, we judge   △ The situation of , To determine whether there is a real root , So let's first define △（disp）

    Step five ： Next, we judge  △ Size , When △ Less than 0 when , The equation has no real root

    Step six ： When △ be equal to 0 when x1 be equal to x2

    Step seven ： When △ Greater than 0 when ,

 

 

 

 

        First step ： frame 

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script>
		
		</script>
	</body>
</html>

        The second step ： We know , The expression of univariate quadratic equation is

                 The root formula is  

 

 

 

So here we need to define x1,x2.a,b,c,△,disp

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script>
			var x1, x2, a, b, c, disp
			
		</script>
	</body>
</html>

      The third step ： We define three variables to receive a,b,c

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script>
			var x1, x2, a, b, c, disp
			var a = prompt(' Please enter a')
			var b = prompt(' Please enter b')
			var c = prompt(' Please enter c')
			
		</script>
	</body>
</html>

                Step four ： Next, we judge   △ The situation of , To determine whether there is a real root , So let's first define △（disp）

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script>
			var x1, x2, a, b, c, disp
			var a = prompt(' Please enter a')
			var b = prompt(' Please enter b')
			var c = prompt(' Please enter c')
			disp = (Math.pow(b, 2) - (4 * a * c))

		</script>
	</body>
</html>

here Math.pow() Is a function that defines the square

        Step five ： Next, we judge  △ Size , When △ Less than 0 when , The equation has no real root 

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script>
			var x1, x2, a, b, c, disp
			var a = prompt(' Please enter a')
			var b = prompt(' Please enter b')
			var c = prompt(' Please enter c')
			disp = (Math.pow(b, 2) - (4 * a * c))

			if (disp < 0) {
				alert(' I'm sorry , The equation has no real root ')
			} 
		</script>
	</body>
</html>

        Step six ： When △ be equal to 0 when x1 be equal to x2

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script>
			var x1, x2, a, b, c, disp
			var a = prompt(' Please enter a')
			var b = prompt(' Please enter b')
			var c = prompt(' Please enter c')
			disp = (Math.pow(b, 2) - (4 * a * c))

			if (disp < 0) {
				alert(' I'm sorry , The equation has no real root ')
			} else if (disp == 0) {
				x1 = (-b / 2 * a)
				x2 = (-b / 2 * a)
				alert('x1=x2 The value is ' + x1)
			}
		</script>
	</body>
</html>

        Step seven ： When △ Greater than 0 when ,

<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
	</head>
	<body>
		<script>
			var x1, x2, a, b, c, disp
			var a = prompt(' Please enter a')
			var b = prompt(' Please enter b')
			var c = prompt(' Please enter c')
			disp = (Math.pow(b, 2) - (4 * a * c))

			if (disp < 0) {
				alert(' I'm sorry , The equation has no real root ')
			} else if (disp == 0) {
				x1 = (-b / 2 * a)
				x2 = (-b / 2 * a)
				alert('x1=x2 The value is ' + x1)
			} else {
				x1 = ((-b + Math.sqrt(disp)) / 2 * a)
				x2 = ((-b - Math.sqrt(disp)) / 2 * a)
			}
			alert('x1 The value of is ' + x1 + '\n' + 'x2 The value of is ' + x2);
		</script>
	</body>
</html>

there Math.sqrt() It means root

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