Screen Resolution Info

Good evening
I just installed Trisquel 7 (yay) on my 2010 Toshiba Sattelite laptop. I found out that my intel wifi wouldn't work so I am currently using a TP-Link usb adapter to browse the net.
However another thing that won't work properly is the screen's resolution. It is set to 1152x824 or something but the proper resolution of the screen should be 1440x900, however this option is not present in the "displays".
I tried to figure it out using google (duh). Installed a package and tried to use the xrandr command but it won't accept the 1440x900 resolution...
Do you have any suggestion how to manage and use the 1440x900 resolution? :(

Thank you in advance