i'm newbie in JQ

i created a show and hide button to open and close div,

i used "simple" code i found on  http://papermashup.com/simple-jquery-showhide-div/

the code working perfectly on my site, but after i click on my botton i want to change the "background image"

i have 2 images, for "show" plus.png and for "hide" minus.png

the original code: works perfect: 

2. jQuery(document).ready(function(){
3. 
   
4. jQuery(".slidingDiv").hide();
5. jQuery(".show_hide").show();
6. 
   
7. jQuery('.show_hide').click(function(){
8. jQuery(".slidingDiv").slideToggle();
9. });
10. 
    
11. });

i add this line 9 for the code so it will show the "hide" background image "minus.png"

see below

2. jQuery(document).ready(function(){
3. 
   
4. jQuery(".slidingDiv").hide();
5. jQuery(".show_hide").show();
6. 
   
7. jQuery('.show_hide').click(function(){
8. jQuery(".slidingDiv").slideToggle();
9. jQuery(".show_hide").css('background-image', 'url(" /andi/images/andi_ua/icons/minus.png ")');
10. });
11. 
    
12. });

its working after i clicked on the the " .show_hide" button, its showing the "minus.png" background image, but how can i code it to show the "show" "plus.png"  if i click on the  " .show_hide" button again ?

please advice ?