Two displays with different resolution are joint

Solution 1:

1. Install arandr

   sudo apt-get install arandr
   

2. Run xrandr.

   If your chosen resolution exists (regardless of which monitor it appears by) then skip the next step

3. If your resolution does not exist, create it by doing the following:

   1. In this example the resolution I want is 1280x1024 cvt 1280 1024. This will create a modeline like this:

      "1280x1024_60.00" 109.00 1280 1368 1496 1712 1024 1027 1034 1063 -hsync +vsync
      

   2. Create the new mode:

      xrandr --newmode "1280x1024_60.00" 109.00 1280 1368 1496 1712 1024 1027 1034 1063 -hsync +vsync
      

4. Add the mode (resolution) to the desired monitor (VGA-1):

   xrandr --addmode VGA-1 "1280x1024_60.00"
   

5. Run arandr and position your monitors correctly

6. Choose 'layout' then 'save as' to save the script

7. I found the best place to load the script (under Xubuntu) is the settings manager:

   xfce4-settings-manager
   

OR

Menu -> Settings -> Settings Manager -> Session and Startup -> Application Autostart

If you have also take problem must comment me.....:)