india ryabha seems mind applications astronomical calculations brahmagupta ce started systematic study indefinite quadratic equations particular misnamed pell equation archimedes may first interested start solved west time fermat euler later sanskrit authors would follow using brahmagupta 's technical terminology general procedure chakravala cyclic method solving pell 's equation finally found jayadeva cited eleventh century work otherwise lost earliest surviving exposition appears bh skara ii 's b ja ga ita twelfth
Formal science Mathematics Pure mathematics Number theory