Mobile solution

Google Nexus 5 Hard Reset

    Press and Hold Volume UP + Volume Down + Power key to get Android Recovery Mode.
    Now you see a word "Start"
    Now Press Volume Down for 2 time to see "Recovery Mode"
    Now press power key to enter Recovery Mode
    Now press Volume UP + Power key to get recovery menu in blue color.
    Now select wipe data/factory reset and press power to confirm selection
    Now select Yes -- Delete all user data and press power to confirm selection
    Now reboot device
    hard reset done