Example: C++ Program to Find the Roots of a Quadratic Equation using sqrt() Function

// C++ Program to Find the Roots of a Quadratic Equation using sqrt() Function
#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;

// `iomanip` header file loaded to print the double value with 2 precision
// `cmath` header file loaded to call the sqrt() function

int main() {
    double p, q, r, d, r1, r2, rp, ip;

    // p, q and r - To store the real numbers
    // d  - To store the discriminant
    // r1 - To store the first root
    // r2 - To store the second root
    // rp - To store the real part
    // ip - To store the image part

    cout << "-----Enter these coefficients a, b and c----\n";
    cin >> p >> q >> r;

    d = q * q - 4 * p * r;
    
    if (d > 0) {
        // It is the condition for real and different roots

        r1 = (-q + sqrt(d)) / (2 * p);
        r2 = (-q - sqrt(d)) / (2 * p);
        cout << "\nThe r1 = " << r1 << " & r2 = " << r2 << "\n";
    } else if (d == 0) {
        // It is the condition for real and equal roots

        r1 = r2 = -q / (2 * p);
        cout << "\nThe r1 = r2 = " << r1 << ";\n";
    } else {
        // if the roots are not real number

        rp = -q / (2 * p);
        ip = sqrt(-d) / (2 * p);
        std::cout << std::fixed << std::setprecision(2) << "\nThe r1 = " << rp << "+" << ip << "i & r2 = " << rp << "-" << ip << "i\n";
    }
    return 0;
}