We know that the profit from an item is the sale price minus the cost price. Thus, 1269 - 0.2x² - 830 - 398x P(x) = -0.2x² - 398x + 439 Local maxima are located at the points where the first derivative of a function are 0 P'(x) = -0.4x - 398 398 = -0.4x x = -995 There is only one maximum so the average value is -995
To answer you get the same denominator so multiply both denominators with each other and do the same with the top so 25 will be at both bottoms and well 15/25 and 8/25. Then solve