Perfect square trinomial means that the constant term is a perfect square, and the middle term is the sum of it's factors.
Option 1: constant 64 sqrt = 8; 8 + 8 = 16 or -8 + -8 = -16 NO
Option 2: constant 36 sqrt = 6; 6 + 6 = 12 or -6 + -6 = -12 NO
Option 3: constant 64 sqrt = 8; 8 + 8 = 16 or -8 + -8 = -16 YES
(x - 8)^2 is the factored form
