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

int N=4;
float A[]={ 2.0,  4.0,  1.0,  2.0,
	    4.0, 14.0, -1.0,  6.0,
	    1.0, -1.0,  5.0, -1.0,
           -4.0,  2.0, -6.0,  1.0};
float b[]={  5.0, 11.0,  9.0, -2.0};
float x[4],det=1.0;

int main()
{
  int i,j,k;

  for(i=0;i<N-1;i++){
    det=det*A[i*N+i];
    if (fabs(det)<0.00005) {
      printf("Hay un cero en la diagonal principal \n");
      return -1;
    }
    for(k=i+1;k<N;k++){
      for(j=i+1;j<N;j++){
        A[j*N+k]=A[j*N+k]-A[i*N+k]*A[j*N+i]/A[i*N+i];
      }
      b[k]=b[k]-A[i*N+k]*b[i]/A[i*N+i];
    }
  }
  for (j=0;j<N;j++){
    for (i=0;i<N;i++){
      printf("A[%d,%d]=%3.2f ",i,j,A[j*N+i]);
    }
    printf("\n");
  }
  return 0;
}