Question 1008473
 R={(x,y):y=x^2}
What is the domain? R X 
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Start with the assumption that "x" is all Real Numbers.
Then look for reasons that would prevent y from
being Real because of some Real value of x.
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In your problem no such x exista, that is y is always Real if x is Real.
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Conclusion
The Domain is "all Real Numbers".
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Cheers,
Stan H.
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