/*
 * Find real roots of quadratic equation:
 * Prompt for coefficients.
 * Print roots if they exist, else message.  Also do simple checking
 * that input is okay.
 *
 * Compile with -lm for sqrt.
 */
#include <stdio.h>
#include <math.h>

int main(void) {
	double a, b, c;
	printf("enter coefficients a, b, c (floating-point)\n");
	if (scanf("%lf %lf %lf", &a, &b, &c) != 3) {
		printf("error:  non-numeric input\n");
		return 1;
	}
	/* check for cases where the formula does not work */
	if (a == 0) {
		if (b == 0) {
			if (c == 0) {
				printf("all coefficients zero, so everything is a root\n");
			}
			else {
				printf("no roots\n");
			}
		}
		else {
			printf("one root %f\n", -c/b);
		}
	}
	else {
		/* compute discrim and test for < 0 (no roots) */
		double discrim = b*b - 4*a*c;
		if (discrim < 0) {
			printf("no real roots\n");
		}
		else if (discrim == 0) {
			printf("one root %f\n", -b / (2*a));
		}
		else {
			printf("two roots %f %f\n", 
					(-b + sqrt(discrim)) / (2*a),
					(-b - sqrt(discrim)) / (2*a));
		}
	}
	return 0;
}