In chapter v of ars magna, cardano gives formulas for solving the different forms of quadratic equations. (this is basically what al-khwarizmi did in his algebra book except cardano's formulas yield both solutions of quadratic equations.) cardano's rule ii is for quadratic equations of the form where the first power is equal to the square and number. let n be the number, a is the coefficient of the first power, and the coefficient of the square is 1. here is cardano's rhetorical solution: multiply one-half the coefficient of the first power by itself and, having subtracted the number from the product, subtract the root of the remainder from one-half the coefficient of the first power or add the two of them, and the value of x will be both the sum and the difference. problem #6: which type of quadratic equation is solved by cardano's solution in #67