The problem of quadratic function The relationship between the price and time t (unit: day) of a certain commodity in the supermarket in the recent 30 days is (T + 10) yuan, and the relationship between the sales volume and time t is (35-t), where t is greater than 0 and less than or equal to 30, and it is an integer. When does the commodity get the maximum daily sales amount? What is the maximum value?
Sales = (T + 10) (35-t) = - T & # 178; + 25t + 350
=-(t-25/2)²+506.25
When t = 12 or 13, the maximum value is 506 yuan