[jQuery] Switch image source during toggle

[Gremlyn1]

I have some divs I am toggling and there is a little + sign image I
want to change to a - sign image when the toggle event occurs, but
can't quite figure it out. Here is the toggle code I have (taken from
a helpful post on here):

$j(document).ready(function() {
    $j('#answerbox').hide();

    $j('a.faq').click(function() {
        var faq_id = $j(this).attr('id');
        $j('#faq' + faq_id).slideToggle("fast");
        return false;
    });
});

The image is not contained within the <a> tag, so I guess I need a
separate function to callback.