Hey guys i am trying to acc captcha protection for 3.8.7 vbulletian forum. I tried very much but failed

I tried this code in header login area.
The Standard Challenge and Non-JavaScript API,
Code:
<script type="text/javascript"
src="http://www.google.com/recaptcha/api/challenge?k=your_public_key">
</script>
<noscript>
<iframe src="http://www.google.com/recaptcha/api/noscript?k=your_public_key"
height="300" width="500" frameborder="0"></iframe><br>
<textarea name="recaptcha_challenge_field" rows="3" cols="40">
</textarea>
<input type="hidden" name="recaptcha_response_field"
value="manual_challenge">
</noscript
>
It show the recaptcha box.But forum looks ugly so i tried regex method of recaptcha buts not working.
The reCAPTCHA AJAX API
Code:
<script type="text/javascript" src="http://www.google.com/recaptcha/api/js/recaptcha_ajax.js"></script>
<!-- Wrapping the Recaptcha create method in a javascript function -->
<script type="text/javascript">
function showRecaptcha(element) {
Recaptcha.create("your_public_key", element, {
theme: "red",
callback: Recaptcha.focus_response_field});
}
</script>
Code:
<div id="recaptcha_div"></div>
<input type="button" value="Show reCAPTCHA" onclick="showRecaptcha('recaptcha_div');"></input>
Doc:
https://developers.google.com/recaptcha/docs/display
Here is the document.Can some one tell me how i can add ? In this big forum there is no plugin for captcha during login lol.So i am trying to make tutorial if i sucess.