Anyone knows why the domain is 0

Question

Anyone knows why the domain is 0 < x < 10 sqrt (2)
plz see the picture attached

anonymous · Answer

attach the picture

anonymous · Answer

just kidding no picture. 
so the question is: the volume of a square-based rectangular cardboard box needs to be 1000cm3. determine the dimensions that require the minimum amount of material to manufacture all six faces. assume that there will be no waste material. the machinery available cannot fabricate material smaller than 2 cm in length

anonymous · Answer

okay so I know how to find the dimensions but the solution also provides a domain which I don't understand: 0 is less than same as x less than same as 10root2

anonymous · Answer

how did they get his domain?

anonymous · Answer

it's all based on 45-45-90 triangle ratios

anonymous · Answer

can you elaborate?