Find the Volume of the cylinder

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Part a: sam rented a boat at $225 for 2 days. if he rents the same boat for 5 days, he has to pay a total rent of $480. write an equation in the standard form to represent the total rent (y) that sam has to pay for renting the boat for x days. (4 points)

The radius of the earth is two times the radius of the moon. what fraction of the volume of the earth is the volume of the moon?