f(x) Members Profile: f(x) Facts and Ideal Types f(x) (에프엑스) was a South Korean girl group that in the last part of their career consisted of 4 members: Victoria, Amber, Luna, and Krystal. f(x) debuted on September 5th, 2009 under SM Entertainment. In August 2015, Sulli officially left the group to concentrate on her acting. In … Continue reading f(x) Members Profile