Displaying the latest post title on a regular home page

I wanted to display the title of the latest post on my blog on my regular home page, which is file “home.php.” This home page is at mywebsite.com/home.php. The blog is at mywebsite.com/blog/. I used the following code, but got an error.

<?php
require('blog/wp-content/themes/amy/header.php');
?>

<?php query_posts('showposts=1'); ?>
<?php while (have_posts()) : the_post(); ?>
<a href="<?php the_permalink() ?>" rel="bookmark" title="Permanent Link to <?php the_title(); ?>"><?php the_title(); ?></a><br />
<?php endwhile;?>

Error message:

Fatal error: Call to undefined function: language_attributes() in /home/server/amy/mywebsite.com/blog/wp-content/themes/amy/header.php on line 2

How do I fix this?