4
1. Cubic Equations
One of the first great advances beyond Arabic mathematics was
taken by Scipione del Ferro (14657-1526), who taught at the Univer-
sity of Bologna at the beginning of the sixteenth century. He was
the first, as reported some decades later by Cardano in his book Ars
Magna,2
to solve general cubic equations, namely those of the type
x3
+ px = q. Without making his method public, del Ferro revealed
it to his student Antonio Fior. At this time, Niccolo Fontana, alias
Tartaglia, was also working on solving cubic equations. Tartaglia,
who was working as a master calculator in Venice, was one of the
best mathematicians in Italy.3 And in fact, he figured out how to
solve cubic equations of the type
x3
+
px2
= q. However, his method
seems to have been less a general solution algorithm than a way of
setting up special equations whose solutions could be easily
found.4
At the competition mentioned at the beginning of the chapter,
Fior posed thirty problems of the type x3 + px = q for Tartaglia
to solve, while conversely, Tartaglia posed thirty somewhat atypical
problems, including cubic equations of the type x3 + px2 = q. At
first, neither contestant could solve any of the problems that he had
been posed. But shortly before the end of the competition, on 13
February 1535, Tartaglia figured out how to solve equations of the
form x3 -f px q. Like del Ferro and Fior, he kept his method of
solution a secret.
And now there enters upon the stage the man whose name is as-
sociated today with the solution formula. Girolamo Cardano, known
today more for his discovery of what is called the Cardano wave and
Cardano suspension and by profession actually a physician, man-
aged to convince Tartaglia to reveal to him his formula, under the
guarantee—according to Tartaglia afterward—that he would keep it
2Girolamo Cardano, The Great Art or the Rules of Algebra, the English transla-
tion of the 1545 edition with additions from the editions of 1570 and 1663 (Cambridge,
Massachusetts, 1968); see the beginning of Chapter 1 and Chapter 11.
3An idea of the accomplishments of a master calculator, and in particular of the
person of Tartaglia, can be found in the historical novel Der Rechenmeister, by Dieter
Jorgensen, Berlin, 1999. A substantial part of the novel deals with the discovery of the
solution formula for cubic equations and the resulting conflict.
4See
the work cited by Renato Acampora, pp. 32-34. On the other hand, based
on the fact that Tartaglia is known to have studied the work of Archimedes, Phillip
Schultz speculates (Tartaglia, Archimedes and cubic equations, Australian Mathemat-
ical Society Gazette 11 (1984), pp. 81-84) that Tartaglia could have used a geometric
method in which he determined the intersection point of the parabola y =
x2
and the
hyperbola y —q/(x + p).
Previous Page Next Page