Series of problems caused by dual-display installation ......

Series of problems caused by dual-display installation ...... -- Linux general technology-Linux technology and application information. For details, refer to the following section. I am familiar with linux and use redhat. The tutor gave me a monitor a few days ago, and I asked my classmates to install it for me. He selected the dual-display Under the display and then restarted. The System Displays X error. Reboot failed. Enter the interface like dos. I saw him cp several xorg. conf. bac files. Then the computer restarts and the display settings return to the position of one monitor. Then he modified the resolution and other things. It seems that he also selected the video card (I don't know whether he finally chose the original video card) and then restarted. As a result, the other monitor turned on (because the single monitor option was selected before He restarted), but both displays the same thing, and because my primary monitor is a 19-inch wide screen, the other is a normal screen of 20, so it is very strange to display ...... That's a big deal. The key is that all the displays do not display the following parts. The taskbar and work zone windows are displayed on the screen. You can find it, but you cannot see it ...... Then, when I try to access the display, the system will not respond.
Tried system-config-display.
Display: X Error of failed request: BadImplementation (server does not implement operation)
Major opcode of failed request: 154 (randroid)
Minor opcode of failed request: 5 (RRGetScreenInfo)
Serial number of failed request: 9
Current serial number in output stream: 9
/Usr/share/system-config-display: line 2: 4279 Segmentation fault python2/usr/share/system-config-display/xconf. py $ @

Now, I'm dumb ...... Hope you can help. Thanks