is a

"is a²-4 prime"

 

Depends on the value of a.  

 

If a = 3, then a² - 4 = 5, which is prime.  

 

If a = 4 then a² - 4 = 12, which is not prime.

.

Is a^2 - 4 prime?

 

If a is an integer > 3, it will be prime. Because if the least value to make it not prime = y, then

 

y - 2 > 1, because we can't let y-2 = 1.

y > 3.

 

If a is an integer < 3 it will be either prime or negative.