There is a passage in the eighth grade mathematics textbook: the square root of the positive number a can be represented by √ a, and the negative square root of the positive number a can be represented by - √ a There is a note beside it saying that the symbol √ A is meaningful only when a ≥ 0, but not when a is less than zero. Why

There is a passage in the eighth grade mathematics textbook: the square root of the positive number a can be represented by √ a, and the negative square root of the positive number a can be represented by - √ a There is a note beside it saying that the symbol √ A is meaningful only when a ≥ 0, but not when a is less than zero. Why

For example, it means that the number a of the root opening sign must be greater than or equal to zero. If a is equal to 4, the root opening sign will have two results - 2 and + 2. If a = - 4, it is meaningless. Negative numbers cannot be root opening