A power with a negative base and an odd exponent is always negative. Therefore, the parentheses can be omitted. $(\text{-} 8)^5=\text{-} 8^5$ The odd exponent means that there are an odd number of negative factors in the product, and the product of each pair is positive. $(\text{-}8)\underbrace{(\text{-}8)(\text{-}8)}_{\text{Positive}}\underbrace{(\text{-}8)(\text{-}8)}_{\text{Positive}}$ This means that the product of all factors except one is positive. And the product of a positive and negative number is always negative. $\text{-} 8\cdot8^4 = \text{-}8^5$