I had my dual monitors working the way I wanted with the Nouveau driver (which is pretty darn good BTW); I installed kernel-3.17 and wound up with both displays presenting the same screens.
Took me a few minutes to figure out what I did to configure them, so, want to pass it on,; really simple:
Start > Favorites > Configure Desktop which will bring up “Display Configuration - System Settings”
When I brought that up, I had a single display shown;
I simply clicked on DVI-I-1 (yours may have a different name) and dragged it to the left, which exposed DVI-I-2 which was hidden under DVI-I-1
using the mouse I aligned them the way I wanted
select your Primary display
Bingo there’s my dual screen using the Nouveau driver.