Implement Newton-Raphson Method using C

/*

 Method of Newton-Raphson

 Equation: x^3-4x-9=0
*/

#include<stdio.h>

void main()
{
 float a,h;
 int i;
 float f(float);
 float f1(float);
 printf("\nEnter initial value:: ");
 scanf("%f",&a);
 for(i=1;i<=5;i++)
 {
  h=-f(a)/f1(a);
  a=a+h;
 }
 printf("\nRoot is:: %f",a);
}
float f(float x)
{
 return (x*x*x)-(4*x)-9;
}
float f1(float x)
{
 return (3*x*x)-4;
}