drivers - Nvidia/Intel hybrid graphics with cinnamon and mdm

I have looked everywhere but i can't seem to find an answer

I Have a laptop (Acer V3-5726-54S6) 1tb 8gbRam with an integrated intel gpu and a Nvidia GT840m(2gb).
Running Ubuntu 14.04 with cinnamon and mdm

i'm trying to get the nvidia card to work with cinnamon using mdm but i can't seem to get it to work.
i've tried

• bumblebee. editing bumblebee.conf. editing xorg.conf.nvidia


• bumblebee with nvidia-340 driver,


• bumblebee with nvidia-331


• bumblebee with nvidia-337


• bumblebee with nvidia-current
  -- nvidia drivers (from website and xorg-edgers ppa)


• nouveau drivers

when i used bumblebee i tried

    $ optirun (any program)

and i got back

[ERROR]Cannot access secondary GPU - error: Could not load GPU driver

[ERROR]Aborting because fallback start is disabled.

this happened on all the different drivers i used (331,337,340,current)
so i uninstalled bumblebee* and nvidia*
tried installing nvidia drivers from the website but that crashes cinnamon.

tried installing the driers without bumblebee (331,340)

selected lightdm when it gave me the option, rebooted, and i got a black screen after boot splash screen. when i chose mdm, cinnamon crashed...

also

$ lspci | egrep 'VGA|3D'

and got back

00:02.0 VGA compatible controller: Intel Corporation Haswell-ULT Integrated Graphics Controller (rev 0b)

03:00.0 3D controller: NVIDIA Corporation GM108M [GeForce 840M] (rev a2)

any help?