√9 = 3
but is it also - 3?
how do i know when a square root is + or -?
Absolutely not!
The real numbers are partitioned into three sets: {negatives}, {0}, & {positives}.
You are confusing two concepts.
So authors insist that 0 is a counting number.
Some say no it is a whole number but not a natural number.
Others disagree with both of those.
But that has nothing to do with 0 being positive. It is not.
Hi, NeedHelp18!
All positive real numbers have two real square roots. However, the radical notation $\displaystyle \sqrt{a}$ generally refers only to the principal square root, which is always the nonnegative value. If you want to represent both square roots, use the notation $\displaystyle \pm\sqrt{a}$. This also applies to $\displaystyle \sqrt[n]{a},\text{ where }n\text{ is even}$. As others mentioned, things get more complicated when you bring complex values into consideration.
And no, Moo, 0 is neither positive nor negative, but it may be included in the set of natural numbers depending on what definition you are using.