Function Keys are not working in my system .The problem is Fedora OS.I have to know how it will be work.

I'm using this command for reducing brightness.
"xrandr --output LVDS1 --brightness .9 "

But it is not much good..So please anybody help me to reduce brightness and working of functional keys

Is this a workstation with external display, or laptop with built-in display? In the former case, you would use the monitor's physical brightness controls. In the latter case, you would use the FN-Key combo that is associated with lowering the display brightness. Personally, after over 25 years of running X-Windows systems, I have NEVER used xrandr to control screen brightness, which is not to say you can't...