To multiply the expressions \( a^{-4} \cdot a^{7} \cdot a^{-9} \), we can use the property of exponents that states \( a^m \cdot a^n = a^{m+n} \).
Now, perform the addition of the exponents:
\[ -4 + 7 + (-9) \]
Calculating this step-by-step:
- \(-4 + 7 = 3\)
- \(3 - 9 = -6\)
Thus, we combine the exponents:
\[ a^{-4} \cdot a^{7} \cdot a^{-9} = a^{-6} \]
Since \( a^{-6} \) can be simplified further using the negative exponent rule \( a^{-n} = \frac{1}{a^n} \):
\[ a^{-6} = \frac{1}{a^6} \]
So the final simplified result is:
\[ \frac{1}{a^6} \]