Algebra/Square Root is Positive
Square Root Is Not Negative
We often say that is the positive number, which when squared is equal to . If this is perfectly correct, but if then which is not positive. So to be technically correct (which is part of the fun of math) we should say that is the non-negative number, which when squared is equal to .
If it is needed to express that a square root may be both positive and negative, you will see .