Every positive number has two square roots, one positive and the other negative.
32=9 so 3 is a square root of 9
(-3)2=9 so -3 is also a square root of 9
In general, every positive number has two square roots. However, a negative number does not have any square roots in the real number system. For example, the number -16 has no square roots because it is imposible to find a real number that when squared gives negative 16. When you square any real number, whether it is positive, negative, or 0, the result cannot be negative.