一种函数的计算方法并给出相应的曲线图片

一种函数的计算方法并给出相应的曲线图片

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<!-- Begin 
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) { 
form.u2.value = -1 * (form.b.value * form.b.value) / (4 * form.a.value) - (-1 * form.c.value); 
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function doCoord(form) { 
form.co.value = form.u.value + "," + form.u2.value; 
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function disc(form) { 
form.o.value = (form.b.value * form.b.value) - (form.a.value * form.c.value * 4); 
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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>