Question

How do you find the domain of `y=sqrt(9+x)`?

Answer 1

Assuming we are restricted to Real numbers
the Domain of `y=sqrt(9+x)` are all Real values of `x` for which this equation is defined (within the Reals).

`sqrt(9+x` is defined for all values `x>=-9`

Therefore the Domain of `y=sqrt(9+x)`
is `[-9,+oo)`