The square root of a negative number, such as \(\sqrt{-9}\), is not possible within the realm of real numbers because there is no real number that, when squared, will yield a negative result. In basic algebra, when a real number is squared, the result is always non-negative, meaning it can either be zero or positive. Therefore, \( \sqrt{-9} \) does not have a real number solution.
However, when considering \(\sqrt{-27}\), we can express this using the concept of imaginary numbers. Any square root of a negative number can be represented using the imaginary unit \(i\), where \(i = \sqrt{-1}\).
For example, we can simplify \(\sqrt{-27}\) as follows:
\[
\sqrt{-27} = \sqrt{27} \cdot \sqrt{-1} = 3\sqrt{3} \cdot i
\]
Hence, \( \sqrt{-27} \) is possible in the context of complex numbers, and it equals \(3\sqrt{3}i\), which indicates that it has a meaningful representation involving imaginary numbers.
In summary, the reason \(\sqrt{-9}\) cannot be computed in real numbers is because it is inherently negative, while \(\sqrt{-27}\) can be expressed using imaginary numbers, making it possible within complex number theory.