Gauss:
#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

using namespace std;

float Gauss(int n,float A[][4],float B[],float X[]){
int i,k,j;
float m,d;
for(i=1;i<=n-1;i++)
for(k=i+1;k<=n;k++)
{m=A[k][i]/A[i][i];
for(j=i;j<=n;j++) A[k][j]=A[k][j]-m*A[i][j];
B[k]=B[k]-m*B[i];
}
d=1;
if(A[n][n]==0) return 1;
for(i=1;i<=n;i++) d=d*A[i][i];
for(i=n;i>=1;i--)
{X[i]=B[i];
for(j=n;j>=i+1;j--) X[i]=X[i]-A[i][j]*X[j];
X[i]=X[i]/A[i][i];
}
return d;
}

int main(int argc, char *argv[]) {
float A[4][4]={{0,0,0,0},{0,3,1,-0.7},{0,0.8,0.7,2},{0,1,3,-0.5}};
float B[4]={0,1,2,3},X[4];
int n=3,i;
cout<<"Determinantul sistemului este"<<Gauss(n,A,B,X)<<endl;
for(i=1;i<=n;i++) cout<<X[i]<<endl;
system("pause");
	return 0;
}

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

using namespace std;

float Jacobi(int n,float A[][4],float B[],float X[]){
int i,j;
float sum;
float Xn[4],Xn1[4];
int sem;
float eps=0.001;
for(i=1;i<=n;i++){
	sum=0;
	for(j=1;j<=n;j++)
    	sum=sum+fabs(A[i][j]);
	if(sum>2*fabs(A[i][i]))
	return 1;}

for(i=1;i<=n;i++)
Xn[i]=X[i];
do{
sem=0;
for(i=1;i<=n;i++)
  Xn1[i]=Xn[i];
for(i=1;i<=n;i++)
{Xn[i]=B[i];
for(j=1;j<=n;j++)
   if(j!=i)
     Xn[i]=Xn[i]-A[i][j]*Xn1[j];
Xn[i]=Xn[i]/A[i][i];
}
for(i=1;i<=n;i++)
if(fabs(Xn[i]-Xn1[i])>eps) sem=1;
}while(sem==1);
for(i=1;i<=n;i++) X[i]=Xn[i];
return 0;}

int main(){
//float A[4][4]={{0,0,0,0},{0,3,1,-0.7},{0,0.8,0.7,2},{0,1,3,-0.5}};
float A[4][4]={{0,0,0,0},{0,3,1,-0.7},{0,1,3,-0.5},{0,0.8,0.7,2}};
float B[4]={0,1,3,2},X[4];
int n=3,i;
if(Jacobi(n,A,B,X)==1)
cout<<"eroare"<<endl;
else
cout<<"Solutiille sunt: "<<endl;
{for(i=1;i<=n;i++) cout<<X[i]<<endl;
system("pause");}

return 0;
}