Home page to show just one category

Hi,
Thanks for the theme! Very good job!
I was wondering if you could tell me how I can show just posts from one category on the home page?
I tried to use : <?php query_posts($query_string . ‘&cat=-5’); ?> on the page.php file on my child theme.
I just have 2 categories so excluding the category 5 would work for me.
But didn’t work.
Any idea? Thanks!