Question

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?

Answer 1

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.