nVidia GTX 870M not detected

[m654321]

I followed your advice Jerry and typed in the following under NVidia Optimus in the Help Manual:

sudo apt-get update
sudo apt-get install nvidia-prime nvidia-331-updates nvidia-settings

After the 2nd line above I get this output...
Reading package lists... Done
Building dependency tree     
Reading state information... Done
Package nvidia is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'nvidia' has no installation candidate
E: Unable to locate package settings
mike@mike-G750JS:~$

So, the presence of the NVidia GPU is being ignored - what can I do now?

Regards
Mike