Square Root of a Negative Number

Everything you need to know about the root of negative numbers is that... it simply does not exist!
Negative numbers do not have a root, if in an exam you come across an exercise involving the root of a negative number, your answer should be that it has no solution.
Want to understand the logic? Keep reading.

The root is some number, let's suppose one that we will call $X$ that, in fact, will be positive and that, when multiplied by itself will give us $X$.
For example, the root of $100$ will be a positive number that if we multiply it by itself we will obtain $100$.
That is, $10$.
Instead of saying "multiply it by itself" we can say "raise it to the square".

As we have seen, the root of any number, for example, $A$ is a positive number that if we square it will give us $A$.
There is no positive number in the whole world that when squared will give us a negative number, therefore, negative numbers do not have a root.

Solve the exercise:
$\sqrt9=3$
If we raise $3$ to the power of two, we will get $9$.
Another exercise
$\sqrt{-9} = No~solution$
We will not be able to find any positive number that, when squared, gives us $-9$ since any positive number squared will be positive and never negative.