Need help wrapping a condition

[Tikila]

thank you for your help in advance.
Would mysql interpret this query properly?

...WHERE type_id='$type_id' AND cat_id='$cat_id' OR maincat_id='$maincat_id' AND item_activated='1' 

I have a GET var that will get either cat_id or maincat_id but all other conditions apply,i want something like this:

WHERE type_id='$type_id' AND (cat_id='$cat_id' OR maincat_id='$maincat_id' ) AND item_activated='1' 

[r937]

i want something like this:

that will work, the first one won't