Uses of wp_insert_user or wp_create_user

Hi all,
i’ve to make a custom register page and i have some problems with
wp_create_user() and wp_insert_user()

Even if i include these files:

include("[my_website_home]/wp-includes/user.php");
include("[my_website_home]/wp-includes/class-wp-error.php");
include("[my_website_home]/wp-blog-header.php");
include("[my_website_home]/wp-load.php");

if I call the function wp_create_user in this way:

$unsafeEmail = $_POST['email'];
$unsafeNome  = $_POST['nomeut'];
$safeEmail = mysql_real_escape_string($unsafeEmail);
$safeNome  = mysql_real_escape_string($unsafeNome);
$safePassword =$_POST['passut'];

wp_create_user($safeNome, $safePassword, $safeEmail);

it has no effect.

And if I try with this:

$unsafeEmail = $_POST['email'];
$unsafeNome  = $_POST['nomeut'];
$safeEmail = mysql_real_escape_string($unsafeEmail);
$safeNome  = mysql_real_escape_string($unsafeNome);
$safePassword =$_POST['passut'];

$user = array(
		'user_login'=>$safeNome,
		'user_pass'=>$safePassword,
		'user_email'=>$safeEmail
);
wp_insert_user($user);

it has no effect.

What I have to include or what is wrong in my code?
Thanks for the replies =)