Example Program - Roots of a Polynomial

Obtaining the Sample Program

The roots of a polynomial a x2 + b x + c = 0 are given by the formula:

x = (-b _ sqrt(b2 - 4ac))/2a

The following program takes as input three double precision numbers, and returns the complex roots as a pair of values.

typedef complex<double> dcomplex;
 
 pair<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);
 }