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 a, b, c;
function xtop(form) {
form.u.value = (form.b.value * -1) / (form.a.value * 2);
}
function ytop(form) {
form.u2.value = -1 * (form.b.value * form.b.value) / (4 * form.a.value) - (-1 * form.c.value);
}
function doCoord(form) {
form.co.value = form.u.value + "," + form.u2.value;
}
function disc(form) {
form.o.value = (form.b.value * form.b.value) - (form.a.value * form.c.value * 4);
}
function zeroes1(form) {
form.n.value = ((form.b.value * -1) - (Math.sqrt(form.o.value))) / (form.a.value * 2);
}
function zeroes2(form) {
form.n2.value = ((form.b.value * -1) - (-1 * Math.sqrt(form.o.value))) / (form.a.value * 2);
}
function move_in(img_name,img_src) {
document[img_name].src=img_src;
}
// End -->
</script>
第二步：把如下代码加入到<body>区域中
<center>
<form>
<table bgcolor="#C0C0C0" cellspacing=2 cellpadding=2 border=3>
<tr>
<td>
<b>
<h3>
<input name="a" size="3">
X<sup>2</sup>+
<input name="b" size="3">
X +
<input name="c" size="3">
<br>
<input type="button" value="x-top" name="x-top" onclick="xtop(this.form)">
<input type="button" value="y-top" name="y-top" onclick="ytop(this.form)">
<input type="button" value="crd" name="crd" onclick="doCoord(this.form)">
<input type="button" value="disc." name="D" onclick="disc(this.form)">
<br>
<input type="button" value="0-points" name="zeroes" onclick="zeroes1(this.form);zeroes2(this.form)">
<input type="button" onclick="xtop(this.form);ytop(this.form);doCoord(this.form);disc(this.form);zeroes1(this.form);zeroes2(this.form)" value="do all">
<input type="button" name="pics" value="show e.g." onClick="if(form.a.value>0 && form.o.value>0)move_in('p','../zh/images/p2.gif');if (form.a.value<0 && form.o.value>0)move_in('p','../zh/images/p3.gif'); if(form.a.value>0 && form.o.value==0) move_in('p','../zh/images/p4.gif'); if(form.a.value<0 && form.o.value==0) move_in('p','../zh/images/p5.gif'); if(form.a.value>0 && form.o.value<0) move_in('p','../zh/images/p6.gif'); if(form.a.value<0 && form.o.value<0) move_in('p','../zh/images/p7.gif')">
<br>
<input type="text" name="u" size="8">
x-top<br>
<input type="text" name="u2" size="8">
y-top<br>
<input type="text" size="8" name="co" onmouseover="form.rem.value=form.co.value">
Coord.<br>
<input type="text" size="8" name="o">
Discriminant<br>
<input type="text" size="8" name="n">
neg zero pt.<br>
<input type="text" size="8" name="n2">
pos zero pt.
<input type="hidden" value="" name="rem">
<br>
<input type="reset" value="reset">
<br>
</h3>
</b> </td>
<td><img src="../zh/images/p1.gif" width=200 name="p" height=200 border=0 alt=""></td>
</tr>
</table>
</form>
</center>
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