#include <stdio.h>

float f(float x);

void search(float xn, float xx, float dx, float tol, float (*f)(float));

float secant(float x1, float x2, float tol, float (*f)(float));

main()

{

float x1, x2, dx, tol;

x1 = -2.0;

x2 = 2.0;

dx = 0.125;

tol = 5.e-5;

search(x1, x2, dx, tol, f);

return 0;

}

void search(float xn, float xx, float dx, float tol, float (*f)(float))

{

float x1, x2;

x1 = xn;

do {

x2 = x1 + dx;

if (f(x1) * f(x2) < 0.0)

printf("a root is %8.5f\n", secant(x1, x2, tol, f));

x1 = x2;

} while (x1 < xx);

}

float f(float x)

{

return x*(x*x-3.0)+1.0;

}