f(x) (Korean: 에프엑스; pronounced /ˌɛf ˈɛks/) is a five member 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 group made their debut on September 1, 2009 with release of a digital single “La Cha Ta” (stylized as “LA chA TA”). The quintet consists of Victoria, Amber, Luna, Sulli and Krystal.
- Victoria (Hangul: 빅토리아) born February 2, 1987 (age 24) as Song Qian (Chinese: 宋茜) (Leader, Vocalist, Main Dancer)
- Amber (Hangul: 엠버) born September 18, 1992 (age 18) as Amber Josephine Liu (Chinese: 劉逸雲) (Main Rapper, Vocalist)
- Luna (Hangul: 루나) born August 12, 1993 (age 17) as Park Sun Young (Hangul: 박선영) (Main Vocalist)
- Sulli (Hangul: 설리) born March 29, 1994 (age 17) as Choi Jin-ri (Hangul: 최진리) (Vocalist, Rapper)
- Krystal (Hangul: 크리스탈) born October 24, 1994 (age 16) as Jung Soo-jung (Hangul: 정수정) (Lead Vocalist)
2009: “La Cha Ta” (Hangul: 라차타; stylized as “LA chA TA”) (released on September 1, 2009)
2009: “Chu” (Hangul: 츄; stylized as “Chu~♡”) (released on November 9, 2009)
2010: “Nu ABO” (Hangul: NU 예삐오) (released on May 4, 2010)
2010: “Mr. Boogie” (released on July 17, 2010)
2011: “Pinocchio (Danger)” (Hangul: 피노키오(Danger)) (released on April 18,2011)
2011: “Hot Summer” (released on June 14, 2011)
2009: “Chocolate Love” (electro-pop version) (released on October 7, 2009)
2010: “Lollipop” (Chinese) (ft. M.I.C) (released on January 2, 2010)
2010: “Thrill Love” OST for “Hungry Romeo, Luxury Juliet” (released on March 17, 2010)
2010: “I Love You, I Love You” OST for “More Charming by the Day” (released on March 21, 2010)
2010: “Calling Out” OST [Luna ft. Krystal] for “Cinderella’s Sister”
2011: “You Are Hiding A Secret” OST for “Paradise Ranch” (released on January 26, 2011)
In late 2009, Luna and Krystal contributed to the soundtrack of television series Invincible Lee Pyung Kang with a duet, “Hard but Easy”. In early 2010, Krystal, Luna and Amber also recorded the song “Spread Its Wings” for the soundtrack of the KBS’s drama, God of Study. Krystal and Luna recorded a duet song for the KBS’s drama Cinderella’s Sister original soundtrack, called “Calling Out”. In late 2010, Luna released a single “Beautiful Day”, as part of the official soundtrack of the KBS drama ‘Please Marry Me’. On December 23, 2010, a duet collaboration between Luna and Super Junior’s Yesung was released, titled “And I Love You“, for the second original soundtrack of KBS’s President.
Krystal appeared on a daily Korean sitcom called “More Charming By The Day” which started from March 22, 2010 to November 2, 2010. The sitcom has total of 138 episodes but Krystal appeared from the 60th episode.
On April 2, 2010, Y-Star started airing first variety show of the group, Hello f(x). The program consisted of four episodes which showed close coverage on their preparations for the first mini-album, Nu ABO. On October 2, 2010, their second reality show, Koala, started airing on MBC’s Every1. The show featured the group’s background life during the SMTown Live ’10 World Tour.
From May of 2010, F(x) members started to appear in variety show on regular basis. Victoria was casted in We Got Married to become a couple with Nichkhun from 2PM. They have been on the show since. She was also casted as regular member of Invincible Youth, and appeared in the show until it ended in December 2010. Luna appeared in Star King and became regular member of the show. She went on to win “New Star” (신인상) award in 2010 SBS Entertainment Award (2010 연예대상). Sulli was casted as the co-host of Inkigayo (인기가요) along with Jo Kwon from 2AM and Jung Yong Hwa of C.N.Blue. She is still hosting the show with Jo Kwon, along with new co-hosts IU and Lee Gi Kwang
In June 2010, Amber rapped in Korean and English for Taiwanese Mandopop artist Danson Tang on track, “I’m Back” from his third album The First Second.
In late 2010, members Victoria, Sulli and Krystal became model endorsers for the clothing brand, Calvin Klein’s X Jeans. A music video for the song, “Beautiful Day”, was released in December 2010 to endorse the brand. The group also endorsed another clothing brand, K-Swiss, for their 2010 winter collection.
In addition to those endorsements, Victoria also was featured in Kangta’s music video of his song 爱，频率 (Love，Frequency).