Final answer:
The square root of -10b implies that b must be less than or equal to zero for the expression to yield a real number since the square root of a negative number is imaginary.
Step-by-step explanation:
The square root of a negative number, such as sqrt of -10b, involves complex numbers since the square root of a negative number is not defined in the set of real numbers.
The symbol 'i' is used to denote the imaginary unit, where i is the square root of -1. To solve the expression for b, you can set up an inequality assuming the square root of -10b must yield a real number (if b were to be a real positive number, this would not be possible since the square root of a positive number times a negative number is imaginary). However, for the completeness of the solution:
If sqrt(-10b) is to be a real number, b must be less than or equal to zero. Therefore, the inequality would be b ≤ 0.