Diophantus was a Greek mathematician who worked in Alexandria around 250 A.D. He was called by some "The Father of Algebra".He wrote a 13 volume treatise on Math of which we have 6 volumes.The other seven volumes have been lost.
Diophantus was the first man that we know of who used letters for variables, developing the synocopated style of writing equations. The Greek letter above is "zeta" which Diophantus used instead of "X."
Diophantus made numerous contributions in the area of algebraic symbolism. However, he only worked with integers. Consequently, Diophantine equations involve only integers as coefficients.
Al-Khwarizmi, also known as, Abu Jafar Muhammad ibn Musa al-Khwarizmi was born in Baghdad, ca 780 AD, a city now in Iraq, around 780 and died around 850. Although there is little information on the life of Al-Khwarizmi, what we do know is rather profound. He is known today as the "father of algebra".