Question 1206522
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The statement of the problem does not use good mathematical language....<br>
My guess as to the meaning of "... for both variables coming from the real number system" is that the set of all real numbers is both the domain and range of the function.<br>
In that case, the relation {{{y=sqrt(x^3)}}}  does not satisfy that condition, because y is not real when x is negative.<br>