Italian mathematician in the 16th century. Raphael Bombelli was the son of a merchant from Bologna and became an engineer (in particular, he drained swamps). He was employed by a Roman, Alessandro Ruffini, to carry out a long project that was interrupted for a few years, which gave him time to write about algebra during the 1560s. He was the first person to use square brackets in his book Algebra. He was one of the great Italian algebraists of the 16th century. He used the four basic operations with complex numbers and he used continuous fractions to calculate square roots and cube roots.