In the beginning of mathematics, Number system was restricted to only integers.
then solutions of equations like $2x=5$ Needed us to extend it to rationals.
then solution of $x^2=\frac{1}{2}$ needed us to extend it to irrational.
Then solutions of $x^2=-1$ needed us to extend it too complex as well.
So considering this analogy solution of $f(x)=a,a \in A$ may not belong to A necessarily, Thus can we not say that numbers beyond complex numbers may exist.
ie. If $f(x)=z,z \in C$ but $x \notin C$
Is there any fundamental theorem which restricts this extension, Are there any clues of this extension, Please discuss and help.