Solve by using the perfect squares method.
x2 + 16x + 64= 0
a. –8
b. –16
c. 8
d. 16

X² + 16x + 64 = 0
x² + 2 * x * 8 + 8² = 0

Now, sing the formula (a + b)² = a² + 2ab + b² , we get,

(x + 8)² = 0

Square rooting on both sides, we get,

x + 8 = √0

x + 8 = 0

x = - 8    <== that's your answer!!!

X²+16x+64=(x+8)² (because (a+b)²=a²+2ab+b² => perfect square)
So you have to find x which will make (x+8)²=0
which is true when x+8=0
x=-8 
That's a.
Hope it helps!

Just a second zzz