24、二元一次方程的解答程序

24、二元一次方程的解答程序

要完成此效果需要两个步骤

 

第一步:把如下代码加入到<head>区域中

 

<SCRIPT LANGUAGE="JavaScript">

<!-- Begin

var rootparti;

var rootpart;

var det;

var rootparti1;

var rootparti2;

var a;

var b;

var c;

var x1;

var x2;

var i = "i";

function checkQuad() {

var a = document.fquad.fa.value;

var b = document.fquad.fb.value;

var c = document.fquad.fc.value;

if (a == 0 && c != 0) {

x1 = -c / b;

x2 = "Not a quadratic equation, but here is your answer for x";

document.fquad.x1.value=x1;

document.fquad.x2.value=x2;

}

else if (a == "" && c != 0) {

x1 = -c / b;

x2 = "Not a quadratic equation";

document.fquad.x1.value=x1;

document.fquad.x2.value=x2;

}

else {

quad();

   }

}

function quad() {

var a = document.fquad.fa.value;

var b = document.fquad.fb.value;

var c = document.fquad.fc.value;

det = Math.pow(b,2) - 4 * a * c;

rootpart = Math.sqrt(det) / (2 * a);

rootparti = (Math.sqrt(-det) / (2 * a)) + i;

if (parseFloat(rootparti) < 0) {

rootparti1 = rootparti;

rootparti2 = (-1 * parseFloat(rootparti)) + i;

}

else {

rootparti1 = (-1 * parseFloat(rootparti)) + i;

rootparti2 = rootparti;

}

if (rootparti1 == "1i") {

rootparti1 = i;

rootparti2 = "-i";

}

else if (rootparti1 == "-1i") {

rootparti1 = "-i";

rootparti2 = i;

}

if (det == 0) {

x1 = x2 = -b / (2 * a);

}

else if (det > 0) {

x1 = (-b + Math.sqrt(det)) / (2 * a);

x2 = (-b - Math.sqrt(det)) / (2 * a);

}

else if ((-b / (2 * a)) == 0) {

x1 = rootparti1;

x2 = rootparti2;

}

else {

x1 = (-b / (2 * a) + " + " + rootparti1);

x2 = (-b / (2 * a) + " + " + rootparti2);

}

document.fquad.x1.value=x1;

document.fquad.x2.value=x2;

}

//  End -->

</script>

 

 

第二步:把如下代码加入到<body>区域中

 

<form name=fquad>

  <table align="center">

    <tr>

<td>

<h2>

<input name=fa size=4>

          <font color="#33FF33">x<SUP>2</SUP>+</font>

          <input name=fb size=4>

          <font color="#33FF33"> x +</font>

          <input name=fc size=4>

          <font color="#33FF33">= 0</font>

          <input type=button value="求值" onClick="checkQuad()">

          

          <input type=reset value="重填">

</h2>

</td>

</tr>

<tr>

<td>

        <h2> <font color="#33FF33">x<sub>1</sub>=</font>

<input name=x1 size=45>

<br>

          <font color="#33FF33">x<sub>2</sub>= </font>

<input name=x2 size=45>

</h2>

</td>

</tr>

</table>

</form>

 

 

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