The restrictions are the x-values that make the denominator equal to zero. It's because you cannot divide anything by 0. It makes the equation undefined.
So, firstly we can factor the denominator, x^2 - 64, and we get (x - 8)(x + 8).
Then, we can use the zero product property to find the x values that make the denominator equal to zero.
x - 8 = 0 x + 8 = 0
+ 8 + 8 - 8 - 8
x = 8 x = -8
The restrictions are x = 8 and x = -8 OR x = ±8