installing new qt on ubuntu code example

Example 1: install qt4-qmake ubuntu

sudo add-apt-repository ppa:rock-core/qt4
sudo apt update
sudo apt install qt4-default
sudo apt install qt4-qmake
#to remove it
sudo add-apt-repository --remove ppa:rock-core/qt4

Example 2: how to install qemu on ubuntu

$ sudo apt-get install qemu-kvm libvirt-daemon-system libvirt-clients bridge-utils