# include <stdio.h>
# include "conio.h"
# include "math.h"
void nhap(float *a, int n,int m);
void xuatmt(float *a, int n,int m);
main()
{ float a[10][10];
 float x[10],m,s;
 char tt;
 int n,i,j,k;
 while (1) {
 printf("\n Nhap n= "); scanf("%d",&n);

 printf("\n Nhap he so cua he phuong trinh:\n");
 for (i=1;i<=n; ++i)
 for (j=1;j<=n+1;++j) {
 printf(" pt[%d%d]=",i,j);
 scanf("%f",&m);
 a[i][j]=m;
 }

 for (i=1;i<=n; i++) {
 printf("\n");
 for (j=1;j<=n+1;j++) printf("%.3f ",a[i][j]);
 }
 /* bien doi A ve ma tran tam giac tren */
 for(i=1;i<n;i++)
 for(j=i+1;j<=n;j++) {
 m=-a[j][i]/a[i][i];
 for(k=i;k<=n+1;k++) a[j][k]+=a[i][k]*m;
 }
 printf("\n");
 for (i=1;i<=n; i++) {
 printf("\n");
 for (j=1;j<=n+1;j++) printf("%.3f ",a[i][j]);
 }
 /* tim nghiem theo qtrinh nguoc */
 for(i=n;i>=1;i--) {
 s=a[i][n+1];
 for(k=i+1;k<=n;k++) s-=a[i][k]*x[k];
 x[i]=s/a[i][i];
 }
 printf("\nNghiem he phtrinh:");
 for(i=1;i<=n;i++) printf("%.3f ",x[i]);
 printf("\n\n Ban tiep tuc ko(c/k)?");
 tt=getch();
 if (tt!='c') break;}
}
/* Ham nhap mang a(m,n)*/
void nhap(float *a, int n,int m)
{ int i,j;
 printf("\n Nhap he so cua he phuong trinh:\n");
 for (i=1;i<=m; i++)
 for (j=1;j<=n;j++) {
 printf(" pt[%d%d]=",i,j);
 scanf("%f",a+i*n+j);
 }
}
/* Ham xuat mang a(m,n)*/
void xuatmt(float *a, int n,int m)
{ int i,j;
 for (i=1;i<=m; i++) {
 printf("\n");
 for (j=1;j<=n;j++) printf("%.3f ",*(a+i*n+j));
 }
}