Set method in a simple c++ class file returning strange values - c++

Question

I am having trouble using a set function in a class file. So far I have the following. I am trying to write a quadratic class that has three private data members and can calculate both the value of a quadratic and the number of real roots in the quadratic. I'm not stuck on the math part as much as I am getting the set methods to not give me weird values. When I test using main, the values for a, b, and c are numbers that I didn't input when I created the object.
Quadratic.hpp
#ifndef QUADRATIC_HPP
#define QUADRATIC_HPP
class Quadratic
{
private:
double a;
double b;
double c;
public:
Quadratic();
Quadratic(double, double, double);
void setA(double);
void setB(double);
void setC(double);
double getA();
double getB();
double getC();
double valueFor(double);
int numRealRoots();
};
#endif
Quadratic.cpp
#include <cmath>
#include <iostream>
Quadratic::Quadratic()
{
setA(1.0);
setB(1.0);
setC(1.0);
}
Quadratic::Quadratic(double A, double B, double C)
{
a = A;
b = B;
c = C;
}
void Quadratic::setA(double A)
{
a = A;
}
void Quadratic::setB(double B)
{
a = B;
}
void Quadratic::setC(double C)
{
c = C;
}
double Quadratic::getA()
{
return a;
}
double Quadratic::getB()
{
return b;
}
double Quadratic::getC()
{
return c;
}
double Quadratic::valueFor(double x)
{
return (a*(pow(x,2)) + b*x + c);
}
int Quadratic:: numRealRoots()
{
double discriminant = pow(b,2) - (4*a*c);
double epsilon = 0.00001;
int realRoots;
if (discriminant <= epsilon && discriminant > 0)
realRoots = 1;
else if (discriminant > epsilon)
realRoots = 2;
else
realRoots = 0;
return realRoots;
}

Answer 1

Your setB method is wrong - it updates a instead of b:
void Quadratic::setB(double B)
{
b = B; // Was "a = B;" in the original code
}