https://help.ubuntu.com/community/WifiDocs/Driver/bcm43xx#Switching_between_drivers
installation steps in below suits my hp 5720s with Broadcom 4312.
b43 - Internet access
12.04 (Precise Pangolin) - 14.04 (Trusty Tahr)
Open a Terminal and if you haven't already done so, update your package list:
sudo apt-get update
If you have a b43 card use the command
sudo apt-get install firmware-b43-installer
internet access scenario means the computer can connect to internet via ethernet cable and accessing repos.
