You may need this: [1]
sudo apt-get -s install --install-recommends linux-generic-lts-trusty linux-image-generic-lts-trusty \ linux-headers-generic-lts-trusty xserver-xorg-lts-trusty libgl1-mesa-glx-lts-trusty
If everything is ok --if and only if-- remove '-s' (stands for simulation). Before reboot!!!, references must be updated: sudo dpkg-reconfigure xserver-xorg-lts-trusty[1] http://askubuntu.com/questions/493541/hardware-enablement-stack-hwe-out-of-support
