You can unfriend someone on Facebook no matter where you are, using the Facebook app for iPhone. The mobile Facebook app doesn't include all Facebook features, but it does give you the ability to unfriend. Whether you're using the iPhone app or your computer's Web browser, after you remove someone from your Facebook friends list on the iPhone, he can no longer post on or access nonpublic areas of your personal Timeline.
Download and install the Facebook app on your iPhone if you don't have it already. Open the App Store and touch "Search," and then type "Facebook" without quotes in the search box. Touch "Facebook" in the search results. Touch the "Free" button and then "Install App" to install the default Facebook app on your iPhone.
Launch the Facebook app from the iPhone home screen and sign in to your account using your Facebook email address and password.
Touch the menu button in the upper-left corner and touch "Friends" to view a list of your Facebook friends.
Touch the name of the friend you wish to unfriend. This action brings up his Timeline. Touch the "Friends" button on his Timeline and select the "Unfriend" option from the menu that opens. When prompted, touch "OK" to confirm your selection.
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