Each student thinks of a non-zero number in his mind, and then calculates it according to the following rules (1), adds 3 to the square, 2) subtracts 9, 3) and divides the difference obtained in the previous step by the number he just thought of to get a quotient. Finally, as long as the obtained quotient is told to the teacher, the teacher can guess what the students are just thinking about. Do you know the secret?

(2) The Environmental Protection Bureau of a city wants to inject all the wastewater from a cuboid wastewater pool with a length of 2* 10 cubic dm, a width of 4* 10 square dm and a height of 8* 10dm into a cubic water storage tank for purification. Would you please consider whether there is a cubic water storage tank to hold these wastewater? If yes, find out the side length of the cubic reservoir; If not, please explain why.