vim /etc/xorg.cong
Section "Monitor"
    Identifier "HDMI-1"
    Option     "PreferredMode" "1600x900"
EndSection
 
Section "Screen"
    Identifier "HDMI-1"
    Monitor          "Monitor"
    DefaultDepth     24
    Option "TwinView Orientation" "RightOf"
 SubSection "Display"
     Depth 24
 EndSubSection
EndSection