False position method ibn Luqa (10th century), an Arab mathematician from Baalbek, Lebanon. He justified the technique by a formal, Euclidean-style geometric proof. Within the tradition of medieval Muslim mathematics, double false position was known as "hisāb al-khaṭāʾayn" ("reckoning by two errors"). It was used for centuries to solve practical problems such as commercial and juridical questions (estate partitions according to rules of Quranic inheritance), as well as purely recreational problems. The algorithm was often memorized with the aid of mnemonics, such as a verse attributed to Ibn al-Yasamin and balance-scale diagrams explained by al-Hassar and Ibn al-Banna, all three being mathematicians of
Midfielder mark specific opposition attackers. Defensive midfielders may also move to the full-back or centre-back positions if those players move forward to join in an attack. Sergio Busquets described his attitude: "The coach knows that I am an obedient player who likes to help out and if I have to run to the wing to cover someone's position, great." A good defensive midfielder needs good positional awareness, anticipation of opponent's play, marking, tackling, interceptions, passing and great stamina and strength (for their tackling). A holding or deep-lying midfielder stays close to their team's defence, while other midfielders may move forward to