flash 制作求函数解析式

stop();
var a:Number;
var k:Number;
var b:Number;
var c:Number;
var d:Number;
d= 0;
function yicihanshu(q:Number):void
{
 xuze.gotoAndStop(2);
 d = 1;
}
yi.addEventListener(MouseEvent.MOUSE_DOWN, yicihanshu);
function fanbilihanshu(q:Number)
{
 xuze.gotoAndStop(1);
 d = 2;
}
fan.addEventListener(MouseEvent.MOUSE_DOWN,fanbilihanshu);
function zhenbilihanshu(q:Number):void
{
 xuze.gotoAndStop(1);
 d = 3;
}
zheng.addEventListener(MouseEvent.MOUSE_DOWN,zhenbilihanshu);
function ercihanshu(q:Number):void
{
 xuze.gotoAndStop(3);
 d = 4;
}
er.addEventListener(MouseEvent.MOUSE_DOWN,ercihanshu);
function jishuan(q:Number)
{
 switch (d)
 {
  case 0 :
   shuchu.text = "先选择函数类型";
  case 1 :
   k=((xuze.Y2.text)-(xuze.Y1.text))/((xuze.X2.text)-(xuze.X1.text));
   b=(xuze.Y1.text)-k*(xuze.X1.text);
   shuchu.text = "y" + "=" + k + "x" + "+" + b;
   break;
  case 2 :
   k=(xuze.X0.text)*(xuze.Y0.text);
   shuchu.text = "y" + "=" + k + "/" + "x";
   break;
  case 3 :
   k=(xuze.Y0.text)/(xuze.X0.text);
   shuchu.text = "y" + "=" + k + "x";
   break;
  case 4 :
   a=(xuze.Y5.text)/(((xuze.X4.text)-(xuze.X5.text))*((xuze.X3.text)-(xuze.X5.text)))
   +(xuze.Y4.text)/(((xuze.X4.text)-(xuze.X5.text))*((xuze.X4.text)-(xuze.X3.text)))
   +(xuze.Y3.text)/(((xuze.X3.text)-(xuze.X4.text))*((xuze.X3.text)-(xuze.X5.text)));
   b=((xuze.Y4.text)-(xuze.Y3.text)-a*((xuze.X4.text)*(xuze.X4.text)-(xuze.X3.text)                                         *(xuze.X3.text)))/((xuze.X4.text)-(xuze.X3.text));
   c=xuze.Y3.text-a*(xuze.X3.text)*(xuze.X3.text)-b*xuze.X3.text;
   shuchu.text = "y" + "=" + a + "x²" + "+" + b + "x" + "+" + c;
 }
}
queding.addEventListener(MouseEvent.MOUSE_DOWN,jishuan);