Simplify. \[ u^{-3} \cdot u^{-9} \] Write your answer with a positive exponent only. \begin{tabular}{ll}\( \square \) & \( \square \) \\ \( \square \) & \( \square \) \\ \hline\end{tabular}

To simplify \( u^{-3} \cdot u^{-9} \), we can apply the property of exponents that states when you multiply two powers with the same base, you add the exponents. Thus, we have: \[ u^{-3} \cdot u^{-9} = u^{-3 + (-9)} = u^{-12}. \] Now, to express this with a positive exponent, we recall that \( u^{-n} = \frac{1}{u^n} \). Therefore: \[ u^{-12} = \frac{1}{u^{12}}. \] Hence, the simplified form is: \[ \frac{1}{u^{12}}. \]