Answer:
The answer is ±8
Explanation
Remember that the answer to a square root is the number that multiplied by himself is equal to the number given----> in this case (64=8·8)
When you have a square root(sqrt) there are two posibble solutions:
A positive one and a negative one
in this case 8·8=64 and (-8)·(-8)=64 so both answers are posible
+√64=8
-√64=-8
±√64=±8