Solving the ax^2+bx+c=0 equation with C language

The solution of ax^2+bx+c=0 equation is obtained by C language.
#include <stdio.h>
#include <math.h>
#define M 0.000001
int main ()
{
float a,b,c,x,x2,n,q,p;
scanf ("%f%f%f", &a,&b,&c);
N=b*b-4*a*c;
if ((a<m) && (a>-m))
{
x= (-c)/b;
printf ("%f", X);
}
else if ((n<m) && (n>-m))
{
x= (-B)/(2*A);
printf ("%f", X);
}
else if (n>0)
{
X= ((-B) +sqrt (n))/(2*A);
X2= ((-B)-sqrt (n))/(2*A);
printf ("%f\n%f", x,x2);
}
Else
{
q= (-B)/(2*A);
P=sqrt (-N)/(2*a);
printf ("%f+%fi\n", q,p);
printf ("%f-%fi\n", q,p);
}
}

Solving the ax^2+bx+c=0 equation with C language