sqrt(x) is a function. It HAS only one answer in formal math. This was
    done just to make things simpler. Its definition is the POSITIVE
    square root. Ask any algebra teacher.

I'm not convinced.  This sounds like one of those on-again off-again
political points that public school systems make a fuss about
teaching "correctly" while anyone who is actually a mathematician
would look at you funny for even suggesting that there was anything
wrong with "i = sqrt(-1)".

And I assume that we are talking about real-world situations.  If you have
real world formulas that involve sqrt(), failing to take the negative root
into consideration can lead to incorrect answers (as I remember one problem
pointing out, much to most of the class's chagrin...)  (Or was that an
equation involving x^2, where you ended up taking sqrt() of both sides?)

And it's "j", damit!

 :-)
BillW