Answer:
The value of y is undefined for values of x that make the denominator of the fraction equal to zero, since division by zero is undefined in mathematics. In this case, the denominator is x - 5, so the value of y is undefined when x - 5 = 0. Solving for x, we get:
x - 5 = 0
x = 5
Therefore, the value of y is undefined when x = 5, since it would make the denominator equal to zero.