To simplify the expression \( (a^3)^{-4} \), you can apply the power of a power rule, which states that \((x^m)^n = x^{m \cdot n}\).
Using that rule:
\[ (a^3)^{-4} = a^{3 \cdot (-4)} = a^{-12} \]
So, the expression \( (a^3)^{-4} \) can be represented as \( a^{-12} \).