this worked on a friends N145
Try the following (from French Ubuntu forum):
sudo add-apt-repository ppa:voria/ppa
sudo apt-get update && sudo apt-get upgrade
sudo apt-get install samsung-tools samsung-backlight
It appears on some systems the function keys begin working but the brightness does not change. In this case, try appending “acpi_backlight=vendor” to the GRUB_CMDLINE_LINUX line in Suspend / Resume below.