Пересечение окружности и прямой

#include <iostream>
#include <cmath>
 
using namespace std;
 
int main(){
    
    double x0;
    cout << "Ââåäèòå x0 = ";
    cin >> x0;
    
    double y0;
    cout << "Ââåäèòå y0 = ";
    cin >> y0;
    
    double r;
    do{
        cout << "Ââåäèòå R = ";
        cin >> r;
    }while (r < 0);
    
    cout << "y = kx + p" << endl;
    
    double k;
    cout << "Ââåäèòå k = ";
    cin >> k;
    
    double p;
    cout << "Ââåäèòå p = ";
    cin >> p;
    
    //ax^2 + bx + c = 0
    
    double a = 1 + k * k;
    double b = 2 * k * (p - y0) - 2 * x0;
    double c = x0 + (p - y0) * (p - y0) - r * r;
    
    double d = b * b - 4 * a * c;
    if (d < 0)
        cout << "Íå ïåðåñåêàþòñÿ" << endl;
    else if (d == 0){
        double x = (-1) * b / (2 * a);
        double y = k * x + p;
        cout << "Ïðÿìàÿ êàñàåòñÿ îêðóæíîñòè â òî÷êå: " << endl;
        cout << "x = " << x << ", y = " << y << endl;
    }else{
        double x1 = (-1) * (b + sqrt(d)) / (2 * a);
        double y1 = k * x1 + p;
        double x2 = (-1) * (b - sqrt(d)) / (2 * a);
        double y2 = k * x2 + p;
        cout << "Ïðÿìàÿ ïåðåñåêàåò îêðóæíîñòü â òî÷êàõ: " << endl;
        cout << "x1 = " << x1 << ", y1 = " << y1 << endl;
        cout << "x2 = " << x2 << ", y2 = " << y2 << endl;
    }
        
    return 0;
}