Xrandr

$ xrandr | grep maximum
Screen 0: minimum 320 x 200, current 1440 x 900, maximum 1680 x 1680

$ gtf 1440 900 59.9
# 1440x900 @ 59.90 Hz (GTF) hsync: 55.83 kHz; pclk: 106.29 MHz
     Modeline "1440x900_59.90" 106.29 1440 1520 1672 1904 900 901 904 932 -HSync +Vsync

neoblitz@n30:~$ xrandr --newmode "1440x900_59.90" 106.29 1440 1520 1672 1904 900 901 904 932 -HSync +Vsync

$ xrandr --addmode VGA 1440x900_59.90 neoblitz@n30:~$ xrandr --output VGA --mode 1440x900_59.90

$xrandr --delmode LVDS1 768x432_59.90
xrandr --rmmode 768x432_59.90

xrandr -s 768x432_59.90