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<HTML><HEAD><TITLE>Example Program - Roots of a Polynomial</TITLE></HEAD>
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<H2>Example Program - Roots of a Polynomial</H2>
<A HREF="sidebar.htm#sidebar77"><IMG SRC="images/note.gif" BORDER=0> <STRONG>Obtaining the Sample Program</STRONG></A>

<P>The roots of a polynomial <SAMP>a x2 + b x + c = 0</SAMP> are given by the formula:</P>
<P><SAMP>x = (-b _ sqrt(b2 - 4ac))/2a</SAMP></P>
<P>The following program takes as input three double precision numbers, and returns the complex roots as a pair of values.</P>
<PRE>typedef complex&#60;double> dcomplex;

pair&#60;dcomplex, dcomplex> quadratic
      (dcomplex a, dcomplex b, dcomplex c)
         // return the roots of a quadratic equation
{
   dcomplex root = sqrt(b * b - 4.0 * a * c);
   a *= 2.0;
   return make_pair(
      (-b + root)/a, 
      (-b - root)/a);
}
</PRE>

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