We do not know the exact date in January of Bombelli's birth, but we are certain that historians credit him with being the first to be brave enough to propose the existence of imaginary numbers and write their rules. We choose to honor him on January 4, as "4" is the only integral root of his historic cubic equation.
Bombelli knew the three real roots were
but if he used only Cardan-Tartaglia, the "state-of-the-art" formula for his time, he would have to convert
to real numbers. Thus, the square root of a negative number could produce three perfectly good solutions.
Please see < http://curvebank.calstatela.edu/bombelli/bombelli.htm >
for a Power Point Slide Show on Bombelli's contributions.
Died: 1572 possibly in Rome, Italy