Hi static,

my laptop specs:
HP Pavilion 15 n029sx
Nvidia GT740m
Intel HD graphics
core i5

I followed procedure from post 1 and till step 15 as I execute command optirun glxspheres64 I got this error

[ 1418.768279] [ERROR]Cannot access secondary GPU - error: X did not start properly

[ 1418.768344] [ERROR]Aborting because fallback start is disabled.
I already tried post #69 where changing

GRUB_CMDLINE_LINUX_DEFAULT="quiet"

to

GRUB_CMDLINE_LINUX_DEFAULT="quiet rcutree.rcu_idle_gp_delay=1"

in /etc/default/grub then update-grub, still I am receiving this error.

I used:
cuda_6.5.14_linux_64.run
NVIDIA-Linux-x86_64-346.35.run
virtualgl_2.4_amd64.deb