Question

Please help: is the square root of -9 a whole number, integer, rational., or irrational?

Answer 1

Explanation:

None of the above.

It is a complex number. The sqrt(-9) is defined as 3i.

i is a definition brought into existence to represent the square root of -1. There is nothing at this level of math that you can point to and say this is the physical thing that is the square root (-1). It is just a math/physics definition.