Go with Anonymous's answer because
not only is 7 an answer because (7)(7) = 49
but also -7 is an answer because (-7)(-7) = 49
(a negative number times a negative number has a positive anwer).
ok there is a lot of confusion here so I will see if I can help to straighten it out for it is quite important.
Firstly 7*7=49 AND (-7)*(-7)=49
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Now if the question is √49 then the answer is 7 (Just 7 NOT -7)
This is because if the square root is written into the original question ONLY the positive answer counts. That is a convention.
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However, if the question is
x2=49findx$Thatisdifferentbecausethesquarerootisnotwrittenintotheoriginalquestion.$x=±√47=±7
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Please, if you want to ask questions do so because this is important.