F(x) was formed as a five-member multi-national K-pop girl group by S.M. Entertainment in 2009. At debut, the group consisted of Victoria, Amber, Luna, Sulli, and Krystal.
Their group name ‘f(x)’ is uniquely written like the mathematical symbol for ‘function’, which portrays the members’ passion to unfold eclectic performances throughout not only Korea but also Asia based on their various talents that could be applied in to the equation as ‘x’, to yield unexpected results.
F(x) was introduced, as the "Asia's Pop Dance Group", through a video teaser released on August 24, 2009.Their debut single, "La Cha Ta", was released on September 1.
On July 25, 2014, SM Entertainment announced Sulli would be taking a temporary hiatus from the Korean entertainment industry. SM announced on August 7th 2015 that Sulli was officially withdrawing from the group and that F(x) would continue as a 4 member group.