1, the grassland is infinitely impossible, and the surface area of the earth is limited, so we can only set the grassland area as a.

2. There can't be an infinite number of sheep. There are so many sheep that the earth is full. Where does the shepherd stand? Therefore, there can only be n sheep in the pasture.

It is impossible to eat all the grass in the pasture. All the other shepherds' sheep have come, but the shepherd still has no place to stand. Therefore, the growth rate of grass in the pasture should be set at V tons/day, and each sheep should eat U tons of grass every day.

Besides being eaten by shepherds, the sheep in the pasture can live forever. There can't be anyone else to eat, and, well, there are wolves to eat. . So we assume that the mortality rate of sheep is d/ day.

5, but also consider the new strength of sheep, the birth rate of sheep.

6. Sheep of different ages eat different grasses.

7. No grass grows in winter. We should also consider the growth rate of grass in different periods.

8, but also consider the input and output.

9. Pay taxes legally.

10, bank loan ~ ~ ~

Simple calculus, complex differential equations.