
 Convergence  How Tartaglia Solved the Cubic Equation 
  And imagine moreover that negative numbers, and also negative solutions of equations, were rejected  called false or fictitious  because then one thought geometrically, and the side of a square, or the edge of a cube cannot be negative. 
  That means, instead of the single cubic equation of today there were not less than 13 equations, 7 with all four terms (cubic, quadratic, linear, and absolute term), 3 without the linear term, and 3 without the quadratic term: 
  But the ten cubic equations containing the quadratic term were too difficult to be solved. 
 mathdl.maa.org /convergence/1/convergence/1/?pa=content&sa=viewDocument&nodeId=1345 (278 words) 
