# FunctionDomain in the Reals numbers [closed]

Why don't I obtain that $x$ belongs to the Reals?

FunctionDomain[x^2 + 4, x]
(* Out: True *)

FunctionDomain[x^2 + 4, x, Reals]
(* Out: True *)


However, there is no problem here:

FunctionDomain[Log[x]/Sqrt[x + y], x]
(* Out: x > 0 && x + y > 0 *)


## closed as off-topic by corey979, MarcoB, m_goldberg, Coolwater, Lukas LangJun 27 '18 at 14:52

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• "This question arises due to a simple mistake such as a trivial syntax error, incorrect capitalization, spelling mistake, or other typographical error and is unlikely to help any future visitors, or else it is easily found in the documentation." – corey979, MarcoB, m_goldberg, Coolwater, Lukas Lang
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• True its mean in this case x \[Element] Interval[{-Infinity, Infinity}]. – Mariusz Iwaniuk Jun 21 '18 at 19:18

FunctionDomain tells you quantitatively what the domain is:
FunctionDomain[Sqrt[x], x]

True just means "no limits" here.