Final answer:
The expression is undefined when substituting the given values into it.
Step-by-step explanation:
The given expression is √(z² - y²). Substituting the given values z = 3 and y = 6 into the expression, we get √(3² - 6²). Evaluating this expression gives √(9 - 36) = √(-27). Since we are working with real numbers, the square root of a negative number is not defined. Therefore, the value of the expression is undefined.
Learn more about Evaluating expressions with given values