Removing glued down particle board from subfloor
You will need to get a Razor floor scraper. 

It takes a little practice to get the angle  that you hold it at in relation to the floor. 

Do not be to aggressive until you get a feel for how well it is removing the glue. Do not go straight at it, angle the blade to patch and gently poke or prod at it, this will result in you getting a little further under it with each poke. Maintain the, just right, angle and keep working at it. 

The glue is strong and you are going to gouge some of plywood but try to minimize this, you can patch later. You may have to come at it from another direction. 

It is not fun, it is hard work. Some floor scrapers work better than others, buy extra blades.