Answer:
We can express the yield per tree as
![y=-6x+780](https://img.qammunity.org/2020/formulas/mathematics/college/2c003z7886kl5b3n04ch1bl8vbeu1ygca0.png)
where y: yield per tree and x: number of trees, with x>75.
Explanation:
With this data we have that:
1) The annual yield per lemon tree is 330 pounds per tree when the number of trees per acre is 75
![y(75)=330](https://img.qammunity.org/2020/formulas/mathematics/college/2b0do6ijje8xz6vptlnu30saotwgiu4k7g.png)
being y the yield per tree.
2) For each additional tree over 75, the annual yield per tree for all trees on the acre decreases by 6 pounds
![(dy)/(dx)=-6](https://img.qammunity.org/2020/formulas/mathematics/college/fuos8v8ynd0q9iu74dt6q2cwzoyqdd3cyp.png)
being x the number of trees.
If we rearrange and integrate we have
![dy=-6dx\\\\\int dy=-6\int dx\\\\y=-6x+C](https://img.qammunity.org/2020/formulas/mathematics/college/erga0u8w1b4iljwx81deg3yhqa795g2cv8.png)
If we use
, we have
![330=-6(75)+C=-450+C\\\\C=330+450=780](https://img.qammunity.org/2020/formulas/mathematics/college/a0gbeknfvrwcvwhwxwy9bduza4wbaxozu0.png)
Then we can express the yield per tree as
![y=-6x+780](https://img.qammunity.org/2020/formulas/mathematics/college/2c003z7886kl5b3n04ch1bl8vbeu1ygca0.png)