f(x) (Korean: 에프엑스; pronounced /ˌɛf ˈɛks/) is a South Korean girl group formed by SM Entertainment in 2009. The name is a play on the mathematical notation for function, with "f" signifying "flower" and "x" representing the female's double X chromosome. The quintet consists of Victoria, Amber, Luna, Sulli, and Krystal.

Krystal was first spotted by SM Entertainment in 2000, which earned her a small role in a short segment of Shinhwa's "Wedding March" music video. Six years later, SM recruited Luna after seeing her performing on a television program.In September 2007, SM discovered Victoria. A month later, Amber was casted from an audition in Los Angeles, California.

While Krystal was the first member to make a media appearance, having appeared briefly in a Lotte commercial in 2002, Sulli was the first member to make a debut, officially debuting as a child actress in September 2005 as the role of young Princess Sun-hwa in the SBS television drama, The Ballad of Seodong.Krystal began training for f(x) in 2006 along with Sulli and Luna.[5] Amber joined them in early 2008


SM first released a teaser preview of the group via YouTube on August 24, 2009, introducing them as "Asia's Pop Dance Group." For five days, SM individually released information through news portals and posted pictures of each member on SM Town's official website, starting with Sulli on August 26..Chinese-American member Amber was revealed on August 27,[3] Korean-American member Krystal on August 28. Luna on August 29, and lastly the other Chinese member Victoria (also the leader) on August 30.

The group's first single "La Cha Ta" (stylized as "LA chA TA") was digitally released on September 1, followed by a 40-second teaser of their music video uploaded to YouTube. Following their first performance at the Samseong-dong Fashion Center on September 2, the music video was screened and released online the next day. The group's first broadcast performance of "La Cha Ta" was held at MBC's music show Show! Music Core on September 5. The group also released the digital single "Chocolate Love" for the 4th edition of the Blacklabel series LG CYON phone, Chocolate, alongside their label mate Girls' Generation. The following month, f(x)'s first EP Chu~♡ was released, consisting of 3 songs. Later that year, Luna and Krystal contributed to the soundtrack of television series Invincible Lee Pyung Kang with a duet "Hard but Easy".

In 2010, the group appeared at the K-POP France show in January. The promotions for Nu ABO ended early caused by Amber spraining her ankle. The group collaborated with Chinese boy band M.I.C. for the song "Lollipop" to promote the LG Cyon phone. Krystal, Luna and Amber also recorded the song "Spread Its Wings" for the soundtrack of the KBS drama God of Study. Krystal and Luna recorded another song for the KBS drama Cinderella's Sister original soundtrack, called "Calling Out". On May 4, 2010, f(x) released their debut mini album Nu ABO, consisting of 6 tracks. Their song "Nu ABO" from the mini album topped online music portal charts Monkey3, Dosirak and Bugs.[citation needed] F(x) also endorse K-swiss. F(x) is now promoting their follow up track "Mr. Boogie" from their mini album "Nu ABO". They had their first performance for this song on July 17, on Music Core.

sursa :Wikipedia

Victoria:


Amber:


Luna:


Sulli:


Krystal: