domain is the set of numbers you are allowed to use for x (or the independendt variable)
x is independent variable here
basically the domain is all real numbers except the ones that cause problems
problem numbers cause division by 0 and square roots by negative numbers
will we have a division by 0 for any real value of x?
no
will we have a square root of a negative nuumber for any real value of x?
no
no 'bad' numbers
domain is all real numbers
