求根和根判别

#include <iostream>
#include <cstdio>
#include <cmath>
using namespace std;

int main()
{
    double a, b, c, r1, r2;
    cin >> a >> b >> c;
    if((b * b - 4 * a * c < 0) || a == 0) printf("Impossivel calcular");
    else
    {
        r1 = (- b + sqrt(b * b - 4 * a * c)) / (2 * a);
        r2 = (- b - sqrt(b * b - 4 * a * c)) / (2 * a);
        printf("R1 = %.5lf\nR2 = %.5lf\n", r1, r2);
    } 
}