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

float eq(float i)
{
	return (pow(i, 3) - (4 * i) - 9); // original equation
}
float eq_der(float i)
{
	return ((3 * pow(i, 2)) - 4); // derivative of equation
}

void main()
{
	float a, b, z, c, m, n;
	clrscr();
	for (int i = 0; i < 100; i++)
	{
		z = eq(i);
		if (z >= 0)
		{
			b = i;
			a = --i;
			goto START;
		}
	}

START:

	cout << "\nFirst initial: " << a;
	cout << "\nSecond initial: " << b;
	c = (a + b) / 2;

	for (i = 0; i < 100; i++)
	{
		float h;
		m = eq(c);
		n = eq_der(c);

		z = c - (m / n);
		c = z;

		if (m > 0 && m < 0.009) // stoping criteria
		{
			goto END;
		}
	}

END:
	cout << "\n\nRoot: " << z;
	getch();
}