secant method

#include<stdio.h>
#include<math.h>
#define E 0.0001
#define f(x) x*x*x*x+2*x*x-16*x+5

void main()
{
    int i=0,n;
    float x1,x2,x3,f1,f2,f3;

    printf("enter number of iterations and initial values x1 and x2\n");
    scanf("%d%f%f",&n,&x1,&x2);
    printf("ITRATION\t  x1\t  x2\t  x3\n");

    while(i<n)
    {

            f1=f(x1);
            f2=f(x2);
            x3=x2-((f2*(x2-x1))/(f2-f1));
            f3=f(x3);

            printf("\n%d\t %.4f\t %.4f\t %.4f ",i+1,x1,x2,x3);

            if(fabs((x2-x1)/x2)<=E)
            {
                printf("\nthe root is %f\n",x3);
                break;
            }

            else
            {
                x1=x2;
                f1=f2;
                x2=x3;
                f2=f3;

            }
            i++;

    }
}


OUTPUT:
enter number of iterations and initial values x1 and x2
100
0
1
ITRATION          x1      x2      x3

1        0.0000  1.0000  0.3846
2        1.0000  0.3846  0.3128
3        0.3846  0.3128  0.3267
4        0.3128  0.3267  0.3265
5        0.3267  0.3265  0.3265
6        0.3265  0.3265  0.3265
the root is 0.326539
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