To simplify the expression \( 5^9 \times 5^{-13} \), we can use the property of exponents that states \( a^m \times a^n = a^{m+n} \).
Here, we have:
\[ 5^9 \times 5^{-13} = 5^{9 + (-13)} = 5^{9 - 13} = 5^{-4}. \]
Now, to express this with only positive exponents, we can use the property that states \( a^{-n} = \frac{1}{a^n} \).
Thus, we can rewrite \( 5^{-4} \) as:
\[ 5^{-4} = \frac{1}{5^4}. \]
Now, let's evaluate the options provided:
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\( 5^9/5^{-13} \): This can be simplified to \( 5^{9 - (-13)} = 5^{9 + 13} = 5^{22} \) but is not equivalent to \( 5^{-4} \).
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\( 5^4 \): This is not equivalent to \( 5^{-4} \).
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\( 1/5^{22} \): This is also not equivalent to \( 5^{-4} \).
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\( 1/5^4 \): This matches \( 5^{-4} \).
Therefore, the equivalent expression to \( 5^9 \times 5^{-13} \) with only positive exponents is
\[ \boxed{1/5^4}. \]