Let $f''(x) = 3 x + 2 x^2.$

(a) Find the most general formula for $f'(x).$ If an arbitrary constant must be used here, use an upper-case "C".

$f'(x) =$

(b) Based on your answer to (a), find the most general formula for $f(x).$ If another new arbitrary constant must be used here, use an upper-case "D".

$f(x) =$