I can't adjust the screen brightness on my HP 2000-2b09WM 15.6-Inch Laptop. Everything is standard on this machine. I have absolutely no idea where to start. Any help would be welcome, as I can only get about 3 hours of battery life as is. I was getting almost 5 hours on windows 8, with the screen as dim as it could get. I use this machine to take notes in school and do assignments between classes, and finding an outlet isn't always an option, but neither is booting back into windows, gross.
edit: I hope this goes without saying, but I've tried the brightness buttons on my keyboard as well as trying to adjust the brightness in the settings. I'm using the cinnamon desktop, if that makes a difference, but the problem is still there with unity.