Given a real number, find the zero of the function. 16. (The full mark of this question is 12) Known function. (i) areas of solution; (2) Confirmation: the function is monotonically increasing in the definition domain. 17. (Full mark in this question 14) The cost of a commodity is 9 yuan, and the price is 30 yuan, and 432 pieces are sold every week. If the price is reduced, the sales volume can be increased, and the number of pieces sold per week is directly proportional to the square of the reduction value of the unit price (unit: yuan). As we all know. (2) How to set the price to maximize the profit of commodity sales in a week? 18. (The full mark of this question is 14) If the function Y = x3-AX2 (A- 1) X 1 in the interval (1 4) is a decreasing function, and in the interval (6, ∞) it is increasing function. 20. (Full score of this question 14) Let the function y= be a function defined on r, which satisfies the following three conditions: ① For any positive number x and y, there are both; ② When x >; When 1, ; 0，∴ 4 ≤ A- 1 ≤ 6。 ∴ 5 ≤ A ≤ 7。 The value range of ∴ A is [5,7]. Comment: If this question is "The function f(x) is a decreasing function on (1, 4)", it is an exploratory question. 19. (The full score of this small question is 14) Solution: (1) It is simplified from the known to ... Because the image is a parabola with a downward opening, it is a function that decreases with time. 14(iii) From the condition (/kloc-0)