Ubuntu 14.04: nvidia drivers for GeForce GTX 960M

I have Ubuntu 14.04 installed on an Asus N551JW laptop with these two graphic cards:

• Integrated Intel® HD Graphics 4600
• NVIDIA® GeForce® GTX 960M 4G GDDR5

By default, Ubuntu recognizes the Intel graphic card but not the NVIDIA one.

When I try to install the Nvidia's drivers I get one of the following errors (depending on how I install drivers):

• Ubuntu freeze in the initial loading screen (before showing the login screen): I get this error if I install drivers from the user interface, going to "Software and Updates" > "Additional Drivers" then selecting the Nvidia drivers (instead of the Nouveau).
• I get a black screen instead of the login screen (I can hear the login alert sound): I get this error using the commands listed below.

So, how to install Nvidia's drivers for my laptop?

What I already tried

I tried as explained here:

How do I install the Nvidia drivers?

Correct nvidia+intel graphics setup in 14.04

these things:

sudo apt-add-repository ppa:xorg-edgers/ppa
sudo apt-get update
sudo apt-get install nvidia-current nvidia-settings

sudo add-apt-repository ppa:bumblebee/stable
sudo apt-get update
sudo apt-get install bumblebee bumblebee-nvidia primus linux-headers-generic

sudo rm /etc/X11/xorg.conf
sudo nvidia-xconfig

But I get the errors described above.

Solution 1:

You did all wrong (almost). Run

sudo apt-get purge nvidia*
sudo apt-get purge bumblebee* primus
sudo add-apt-repository ppa:graphics-drivers/ppa
sudo apt-get update
sudo apt-get install nvidia-352 nvidia-prime
sudo add-apt-repository -r ppa:bumblebee/stable

and hope that you did not spoil everything completely with previous attempts.