quartic.h

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#ifndef QUARTIC_H
#define QUARTIC_H

namespace tag {

inline double eval_quartic(double B, double C, double D, double E, double x)
{
    return E + x*(D + x*(C + x*(B + x)));
}

inline double newton_quartic(double B, double C, double D, double E, double x)
{
    double fx = E + x*(D + x*(C + x*(B + x)));
    double dx = D + x*(2*C + x*(3*B + x*4));
    return x - fx/dx;
}

int find_quartic_real_roots(double B, double C, double D, double E, double r[]);

}

#endif