Urgent need for an answer .............................................................................................................................................................................

Ls's answer is very powerful ~ haha

Let y be the profit and x be the number of days when selling, then the following equation can be listed:

y =(80+2x)*(8-0. 1x)-5x = -0.2x^2+3x+640

To find the maximum value of y, there are two methods:

1. derivative

When the derivative is 0, y has the maximum value.

Let y'=-0.4 x+3 = 0, and x = 7.5 is obtained.

Where x = 7 and y = 65 1.2.

Where x = 8 and y = 65 1.2.

Therefore, the maximum profit of 65 1.2 can be obtained by selling on the 7th or 8th day.

Step 2: Formula

y = -0.2(x - 7.5)^2 + 65 1.25

According to the nature of parabola, there is the highest point.

It is also known later that when x = 7 or 8, there is a maximum value of 65 1.2.

With the liberalization of the second child policy, many families now have two children, but many problems that follow are gradually exposed.