QZ: 3) Find two positive numbers x and y such that x + 2y = 50 and (x + 1)(y + 2) is a maximum. b) Consider the function f(x) = 3x5 20x3. i. Find the intervals where the function is increasing, decreasing. ii. Find the local maximum and minimum points and values. iii. Find the inflection points. iv. Find the intervals where the function is concave up, concave down. v. Sketch the graph ofthe function