Please help me, if I get this wrong I fail.

Atoy company is considering a cube or sphere-shaped container for packaging a new product. the height of the cube would equal the diameter of the sphere . compare the volume to surface area ratios of the containers. which packaging will be more efficient? for a sphere, sa =4πr²

How do you solve a question like this?

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