To solve the equation \( 2x = -4 \), we first need to isolate \( x \).
- Divide both sides by 2: \[ x = \frac{-4}{2} = -2 \]
Now that we have \( x = -2 \), we need to find the value of \( 8x \):
- Multiply \( x \) by 8: \[ 8x = 8(-2) = -16 \]
Therefore, the value of \( 8x \) is \( \boxed{-16} \).