Were Brahmagupta and Alī ibn Abī Ṭālib alive at the same time?
Yes. Brahmagupta and Alī ibn Abī Ṭālib were alive at the same time, from c. AD 598 to AD 661.
Alī ibn Abī Ṭālib was about a year old when Brahmagupta was born.
Alī ibn Abī Ṭālib
4th Rashidun Caliph (r. 656–661) and first Shia Imam
Born 17 March AD 599 · died AD 661, aged 61 or 62