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

float f(float x)
{
      return (pow(x,3)-4*x-9);
}

void main( )
{
    float a=-1.0, b=0.0, x=0.0, y=0.0, err;
    while(f(a)*f(b)>0)
    	{
      	   a=b;
     	   b=b+1.0;
    	}
printf(“Enter the error: “);
scanf(“%f”,&err);
printf("\n\troot lies between: %f and %f",a,b);
printf("\n\n\t  a(-ve)\tb(+ve)\t\t    x\t\t      f(x)");
printf("\n\t-------------------------------------------------------------\n");
    	 //*swapping the values*//

  	  if(f(a)>0)
    	{
     		 a=a+b;
     		 b=a-b;
      		 a=a-b;
    	}
 //* Finding the approximate value of the root*//

  	  do
     	 {
       	  y=x;
       	  x=(a+b)/2;
        	  if(f(x)<0)
          	 a=x;
       	  else
         	  b=x;
          	printf("\n\t%f\t%f\t%f\t  %f",a,b,x,f(x));
      	}while(fabs(x-y) > err);

printf("\n\t-------------------------------------------------------------\n");
          	printf("\n\tAnswer: %.4f  (correct upto 4 decimal places)",x);

      getch( );
}