Answer:
5 more than 30 trees should be planted, for a total of 40 trees per acre.
Step-by-step explanation:
Let x be the number of trees beyond 30 that are planted on the acre
The number of oranges produced = Oranges(x) = (number of trees) (yield per
tree)
We are given that For each additional tree in the acre, the yield is reduced by 7 oranges per tree
So, number of oranges produced =![(30 + x)(400 -10x)](https://tex.z-dn.net/?f=%2830%20%2B%20x%29%28400%20-10x%29)
= ![12000 -300x+400x-10x^2](https://tex.z-dn.net/?f=12000%20-300x%2B400x-10x%5E2)
= ![12000 + 100x-10x^2](https://tex.z-dn.net/?f=12000%20%2B%20100x-10x%5E2)
The derivative Oranges'(x) =
100-20x
Substitute first derivative equals to 0
![100-20x =0](https://tex.z-dn.net/?f=100-20x%20%3D0)
![x=5](https://tex.z-dn.net/?f=x%3D5)
Using the second derivative test,
Oranges"(x) = -20
20 is negative,
So, this is the case of maximum.
Thus, 5 more than 30 trees should be planted, for a total of 40 trees per acre.