一种函数的计算方法并给出相应的曲线图片

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var a, b, c;
function xtop(form) {
form.u.value = (form.b.value * -1) / (form.a.value * 2);
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function ytop(form) {
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<form>
<table bgcolor="#C0C0C0" cellspacing=2 cellpadding=2 border=3>
<tr>
<td>
<b>
<h3>Parabolic Calculator</h3>
<input name="a" size="3">X²+
<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@#,@#p2.gif@#);if (form.a.value<0 && form.o.value>0)move_in(@#p@#,@#p3.gif@#); if(form.a.value>0 && form.o.value==0) move_in(@#p@#,@#p4.gif@#); if(form.a.value<0 && form.o.value==0) move_in(@#p@#,@#p5.gif@#); if(form.a.value>0 && form.o.value<0) move_in(@#p@#,@#p6.gif@#); if(form.a.value<0 && form.o.value<0) move_in(@#p@#,@#p7.gif@#)" value="show e.g.">
<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>
</b>
</td>
<td><img src="p1.gif" width=200 name="p" height=200 border=0 alt=""></td>
</tr>
</table>
</form>

原文转自：http://www.ltesting.net