Problem: ( 3 x + 1 ) ( 2 x - 5 ) = ax ^ 2 + kx + n . what is the value of a - n + k ?
Rationale: "expanding we have 6 x ^ 2 - 15 x + 2 x - 5 6 x ^ 2 - 13 x - 5 taking coefficients , a = 6 , k = - 13 , n = - 5 therefore a - n + k = 6 - ( - 13 ) - 5 = 19 - 5 = 14 the answer is d ."
annotated_formula: add(add(multiply(3, 1), multiply(5, 1)), subtract(multiply(1, 1), multiply(5, 3)))