Final answer:
The square root of a negative number is not defined in the set of real numbers, but can be evaluated in the set of complex numbers by using the imaginary unit i. The simplified form of √(-64) is 8i.
Step-by-step explanation:
When simplifying √(-64), we first notice that the number under the square root sign is negative. However, the square root of a negative number is not defined in the set of real numbers.
However, in the set of complex numbers, we can evaluate the square root of a negative number by using the imaginary unit i, where i = √-1.
Therefore, the simplified form of √(-64) is 8i (option a).