ubuntu - Not able to connect an external monitor

I am new to ubuntu and I am facing this behavior and don't know what to do. I would appreciate any help.

I am trying to connect external monitor via VGA(I tried even via HDMI,but no use) but not able to connect external monitor in my laptop. I don`t see any option in system settings or any where. I guess my laptop is not detecting external monitor.

When I give xrandar while external monitor is connected, I am getting following error

 xrandr: Failed to get size of gamma for output default
 Screen 0: minimum 1366 x 768, current 1368 x 768, maximum 1368 x 768
 default connected 1368x768+0+0 0mm x 0mm
   1366x768        0.0
   1368x768        0.0*

I am stuck in this issue.

I am using Ubuntu 12.04 and KDE plasma desktop and my laptop model is DELL latitude E5530.

Can somebody create some diagnoses and give some possible solution, please?