To simplify the expression \( 5^9 \cdot 5^{-13} \) using the properties of exponents, we can use the rule that states \( a^m \cdot a^n = a^{m+n} \).
So, we calculate:
\[ 5^9 \cdot 5^{-13} = 5^{9 + (-13)} = 5^{-4} \]
Next, we need to express this with only positive exponents. We can change \( 5^{-4} \) to positive exponent form by using the property \( a^{-n} = \frac{1}{a^n} \):
\[ 5^{-4} = \frac{1}{5^4} \]
Now, looking at your options, we see that the equivalent expression with only positive exponents is:
\[ 1/5^4 \]
Thus, the correct response is 1/5^4.