▁way ▁of ▁solving ▁quart ic ▁equations , ▁but ▁Ferr ari ' s ▁method ▁dep ended ▁upon ▁T art aglia ' s , ▁since ▁it ▁involved ▁the ▁use ▁of ▁an ▁auxili ary ▁cub ic ▁equation . ▁Then ▁Card ano ▁became ▁aware ▁of ▁the ▁fact ▁that ▁Sci p ione ▁del ▁Fer ro ▁had ▁discovered ▁T art aglia ' s ▁formula ▁before ▁T art aglia ▁himself , ▁a ▁discovery ▁that ▁prompt ed ▁him ▁to ▁publish ▁these ▁results . ▁ ▁Cont ents ▁The ▁book , ▁which ▁is ▁divided ▁into ▁forty ▁chap ters , ▁contains ▁the ▁first ▁published ▁algebraic ▁solution ▁to ▁cub ic ▁and ▁quart ic ▁equations . ▁Card ano ▁acknowled ges ▁that ▁T art aglia ▁gave ▁him ▁the ▁formula ▁for ▁solving ▁a ▁type ▁of ▁cub ic ▁equations ▁and ▁that ▁the ▁same ▁formula ▁had ▁been ▁discovered ▁by ▁Sci p ione ▁del ▁Fer ro . ▁He ▁also ▁acknowled ges ▁that ▁it ▁was ▁Ferr ari ▁who ▁found ▁a ▁way ▁of ▁solving ▁quart ic ▁equations . ▁ ▁Since ▁at ▁the ▁time ▁negative ▁numbers ▁were ▁not ▁generally ▁acknowled ged , ▁knowing ▁how ▁to ▁solve ▁cub ics ▁of ▁the ▁form ▁x 3   +   ax   =   b ▁did ▁not ▁mean ▁knowing ▁how ▁to ▁solve ▁cub ics ▁of ▁the ▁form ▁x 3   =   ax   +   b ▁( with ▁a , b   >   0 ), ▁for ▁instance . ▁Besides , ▁Card ano , ▁also ▁explains ▁how ▁to ▁reduce ▁equations ▁of ▁the ▁form ▁x 3   +   ax 2   +   b x   +