codice:
$(function(){
    $('.box_1').hide();
    $('#ico_1,#ico_2').toggle(
    function(){
        var box_class=$(this).attr('id').replace('ico','box'); 
        $('.'+box_class).slideDown(600); //sarebbe meglio usare un id
        $(this).attr("src","http://cdn2.iconfinder.com/data/icons/fugue/icon/toggle.png");
    },
    function(){
        var box_class=$(this).attr('id').replace('ico','box');
        $('.'+box_class).slideUp(800); 
        $(this).attr("src", "http://cdn4.iconfinder.com/data/icons/fugue/icon/toggle-expand.png");
    }
    );
});