added zero

exemples/zero.c

+#include <stdio.h>
+#include <math.h>
+#include <stdlib.h>
+
+double f(double x) {
+    return x * x - 25.0;
+}
+
+double next_x(double x1, double x2, double (*foo)(double)) {
+    return x1 - (x2-x1)/(foo(x2)-foo(x1))*foo(x1);
+}
+
+int main() {
+    const int max_iter = 1000;
+    double x1 = rand();
+    double x2 = rand();
+    printf("x1 = %f, x2 = %f\n", x1, x2);
+    for (int i = 0; i < max_iter; ++i) {
+        double x3 = next_x(x1, x2, f);
+        x1 = x2;
+        x2 = x3;
+        printf("x3 = %f, f(%f) = %f, at iter = %d\n", x3, x3, f(x3), i);
+        if (fabs(f(x3)) < 0.00001 ) {
+            return EXIT_SUCCESS;
+        }
+    }
+    return EXIT_FAILURE;
+}
\ No newline at end of file