Quadratic formula solver in C

Code:

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

int main(int argc, char *argv[])
{
	double a, b, c, x1, x2;
	a = 0; b = 0; c = 0;
	if(!(argv[1])||(argv[1][0]=='/'&&argv[1][1]=='?'))
	{
		printf("QUAD A B C\nTo solve quadratics in the form 

Ax^2+Bx+C=0");
		return 0;
	}
	if(argc!=4)
	{
		printf("Usage error: Must be QUAD a b c for any quadratic 

ax^2+bx+c=0");
		return 0;
	}
	a = strtod(argv[1],0);
	b = strtod(argv[2],0);
	c = strtod(argv[3],0);
	if(a==0)
	{
		printf("A cannot be 0");
		return 0;
	}
	//printf("%f %f %f\n",a,b,c);
	if(((b*b)-(4*a*c))<0)
	{
		printf("Nonreal roots\n");
		return 0;
	}
	x1 = (-b+sqrt((b*b)-(4*a*c)))/(2*a);
	x2 = (-b-sqrt((b*b)-(4*a*c)))/(2*a);
	printf("x[1] = %f\n",x1);
	printf("x[2] = %f\n",x2);
	return 0;
}

I know that the checking for whether argv[1] = "/?" was a little crude but other than that it's awesome, I think.