wp_get_attachment_image – Last image returned from post

Hi Team,

i am using below code for generate images in feed,

function show_image_feed($content) {

global $post;
$args = array(
'post_type' => 'attachment',
'numberposts' => 1,
'post_status' => null,
'post_parent' => $post->ID
);

$attachment = get_posts($args);

if ($attachment) {

 $content =  wp_get_attachment_image($attachment[0]->ID, 'medium') .'<p>'. $content . '</p>' . '<br />';
}

return $content;

}

add_filter('the_excerpt_rss', 'show_image_feed'); // for feed excerpts
add_filter('the_content_feed', 'show_image_feed'); // for full feeds

I included two images into the post one at the top and another one in bottom. but in the feed the bottom images is displayed first in the content part, i need first (top) image of the post.

What i need to do?