// roots(a, b, c, r1, r2) - returns the number of 
// real roots of ax^2 + bx + c. If two roots exists
// they are returned is r1 and r2. If only one root
// exists, it is returned in r1. Otherwise the value
// of r1 and r2 is undetermined.

extern int roots(float a, float b, float c, float& r1, float& r2);