To simplify the expression \( 3^7 \cdot 3^{-9} \) using the properties of integer exponents, we can apply the property that states \( a^m \cdot a^n = a^{m+n} \).
- Combine the exponents:
\[ 3^7 \cdot 3^{-9} = 3^{7 + (-9)} = 3^{7 - 9} = 3^{-2} \]
- Convert to positive exponents:
To express \( 3^{-2} \) with a positive exponent, we use the property \( a^{-n} = \frac{1}{a^n} \):
\[ 3^{-2} = \frac{1}{3^2} \]
- Calculate \( 3^2 \):
\[ 3^2 = 9 \]
- Write the final answer:
\[ 3^{-2} = \frac{1}{9} \]
Thus, the simplified expression \( 3^7 \cdot 3^{-9} \) equals \( \frac{1}{9} \).