How come when you're rationalizing to evaluate a limit and you get a a square root with a numerical answer inside, you always take the +ve root? ie: √9 = 3, never -3?

Question

amtran_bus · Answer

Taking the root of a negative number is impossible, for example $$\sqrt{-9}$$
$$3^2$$ equals nine, as well as $$-3^2$$, equals a positive nine.  But when you square a number to get 9, it always results in a positive answer, and this is just the reverse process.