// Решение уравнения a*x^2 + b*x + c = 0

#include <stdio.h>
#include <math.h>

double a, b, c;
double x1, x2;

void sqroot() {
    
    if(a == 0.0) {
        if(b == 0.0) {
            if(c == 0.0) {                          // 0 = 0
                printf("Infinite number of roots (0 = 0)\n");
            } else {                                // c = 0
                printf("No roots (c = 0)\n");
            }
        } else { // b != 0
            if (c == 0) {                           // b * x = 0
                printf("x1 = x2 = 0 (b * x = 0)\n");
            } else {                                // b*x + c = 0
                x1 = x2 = -c / b;
                printf("x1 = x2 = %lf (b*x + c = 0)\n", x1);
            }
        }
    } else { // a != 0
        if (b == 0.0) {
            if(c == 0.0) {                          // a * x^2 = 0
                printf("x1 = x2 = 0 (a * x^2 = 0)\n");
            } else {                                // a * x^2 + c = 0
                x1 = (-c) / a;
                if(x1 > 0) {  // -c/a > 0
                    x1 = sqrt(x1);
                    x2 = -x1;
                    printf ("x1 = %lf, x2 = %lf (a * x^2 + c = 0)\n", x1, x2);
                } else { // -c/a < 0
                    printf("No roots (a * x^2 + c = 0)\n");
                }
            }
        } else {
            if(c == 0.0) {                          // a * x^2 + b * x = 0
                printf("x1 = 0, x2 = %lf (a * x^2 + b * x = 0)\n", -b / a);
            } else {                                // a * x^2 + b* x + c = 0
                double d = b*b - (a + a)*(c +c);
                if(d < 0.0) {
                    printf("No roots (a * x^2 + b* x + c = 0)\n");
                } else { 
                    if(d == 0) { // a != 0.0 && b
                        x1 = x2 = -b / (a+a);
                        printf ("x1 = x2 = %lf a * x^2 + b* x + c = 0\n", x1);
                    } else { // d > 0
                        d = sqrt(d);
                        x1 = (-b - d) / (a+a);
                        x2 = (-b + d) / (a+a);
                        printf ("x1 = %lf, x2 = %lf (a * x^2 + b* x + c = 0)\n", x1, x2);
                    }
                }
            }
        }
    }
    return;
}

int main() {
    printf("a? ");
    scanf("%lf", &a);

    printf("b? ");
    scanf("%lf", &b);

    printf("c? ");
    scanf("%lf", &c);
    
    printf("%lf * x^2 + %lf * x + %lf\n", a, b, c);
    
    sqroot();
    
    printf("test value1 = %lf\n", a * x1 * x1 + b * x1 + c);
    printf("test value2 = %lf\n", a * x2 * x2 + b * x2 + c);

    return 0;
}