Use o nano para editar seu arquivo sources.list:
sudo nano /etc/apt/sources.list
Agora use CTRL + K para apagar todas as linhas do arquivo.
Em seguida, coloque as seguintes linhas no arquivo:
deb http://archive.ubuntu.com/ubuntu/ trusty main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ trusty main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ trusty-updates main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ trusty-updates main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ trusty-backports main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu trusty-security main restricted universe multiverse
deb-src http://security.ubuntu.com/ubuntu trusty-security main restricted universe multiverse
deb http://archive.canonical.com/ubuntu trusty partner
deb-src http://archive.canonical.com/ubuntu trusty partner
Pressione CTRL + o para salvar o arquivo, pressione CTRL + x para sair do nano.
Execute os seguintes comandos:
sudo apt-get update
sudo apt-get install nvidia-352
Reinicie.
Por favor, poste qualquer erro.