Tinh can bac 2 theo phuong phap lap newton

#include <stdio.h>
#include <math.h>
#include<conio.h>
void main()
{
double a, xn, ketqua;

printf("\nNhap vao so muon tinh can bac hai : ");
scanf("%lf", &a);
xn = (a+1)/2;
do {
ketqua = xn;
xn = 0.5 * (xn + a/xn);
} while (fabs(xn-ketqua) > 0.0001);
printf("\nKet qua = %.1lf", xn);
getch();
}