Answer:
-9
Step-by-step explanation:
x² -16 = (x -4)(x +4)
This magnitude of this product can only be prime if one of the factors is ±1. Any other integer value of x will produce a composite number (or zero).
... For x-4 = ±1, x = 3 or 5
... For x+4 = ±1, x = -3 or -5
The values of x that are ±3 both give |x²-16| = 7, a prime.
The values of x that are ±5 both give |x²-16| = 9, not a prime.
The two values of x that are of interest are x=-3 and x=3. Their product is ...
... (-3)·(3) = -9
