Duplicate monitors on multi-screen setup without mirroriing all?

[mosritemecha]

Hey guys, I have a 3 monitor setup (well, two monitors and a TV) and the way I had it set up in Windows was to duplicate my main monitor on the TV (3rd screen) while using 1 and 2 as a multi-monitor desktop. The default setting options in Mint only seem to give me the option of mirroring the display on all 3, or using each as a separate monitor. I thought maybe there's an application out there with more robust display options, but couldn't find anything looking through the software manager - am I missing something or is this just not an option in Mint?

[FreedomTruth]

the terminal program xrandr should do this (I haven't used it with more than 2 monitors so I won't swear to it)
first run xrandr with no arguments to get the output names
then run something like this, adjusting it for your system, xrandr --output HDMI-3 --same-as HDMI-1 --auto