Hi Student!
This question can seem quite complex but it has a simple explanation. Just imagine, what is the purpose of a square root? It shows what can by multiplied against itself and produce the number that is in the square root. That is why when we take the square root of 4 we get 2 and -2 because they both produce the number 4 when we square them. Whenever we square a number, no matter if it's positive or negative, the answer will always be positive. This is because in order to get a negative number only one can be negative to overcome the positive otherwise it's just a double negative.
Therefore, there is a solution to the question of what is the square root of -4. What we do is practically take out the negative because the square root of -1 is equal to i. So we take the following steps
Separate the square root
Simplify the expression
Looking at what we have done, we see that although the explanation behind it might seem complex the actual solving portion isn't too hard when explained. Therefore, the solution to the square root of -4 would be 2i.