To vertically compress the function \( y = 9(5)^x \) by a factor of \( \frac{1}{3} \), you multiply the entire function by \( \frac{1}{3} \).
The original function is:
\[ y = 9(5)^x \]
To apply the vertical compression, we rewrite the function as:
\[ y = \frac{1}{3} \cdot 9(5)^x \]
Now, simplifying this gives:
\[ y = 3(5)^x \]
So, the new function after vertically compressing by a factor of \( \frac{1}{3} \) is:
\[ y = 3(5)^x \]