In fact he had discovered in 1543 that Tartaglia was not the first to solve the cubic equation by radicals and therefore felt that he could publish despite his oath. Ferrari wrote in April 1547:
Sa katunayan siya ay natuklasan sa 1543 na Tartaglia ay hindi ang unang upang malutas ang kubiko equation ng mga radicals at sa gayon ay madama na siya ay ilathala sa kabila ng kanyang panunumpa. Ferrari wrote in April 1547: