To rewrite the expression \((8^5)^9\) as \(8\) raised to a single power, you can use the property of exponents that states \((a^m)^n = a^{m \cdot n}\).
Applying this property:
\[ (8^5)^9 = 8^{5 \cdot 9} \]
Now, calculate \(5 \cdot 9\):
\[ 5 \cdot 9 = 45 \]
Thus, the expression can be rewritten as:
\[ (8^5)^9 = 8^{45} \]
So the final answer is:
\[ 8^{45} \]