The equation 6x3 = 43x2 + 79x is solved in the Summa of Luca Pacioli as follows; "Add the number to the cose to form a number, and then you get one cubo equal to 7 1/6 censi plus 18 1/6, after you have reduced to one cubo [divided all the terms by 6]. Then divide the censi in half and multiply this half by itself, and add it onto the number. It will be 31/1/144 and the cosa is equal to the root on this plus, which is half of censi
Show that Pacioli's answer is incorrect. What was he thinking of in presenting his rule?