To use the Negative Exponent Rule, we remember that \( a^{-n} = \frac{1}{a^n} \).
Applying this rule to the expression \( 3^{-1/2} \):
\[ 3^{-1/2} = \frac{1}{3^{1/2}} = \frac{1}{\sqrt{3}} \]
So, the equivalent expression to \( 3^{-1/2} \) is \( \frac{1}{\sqrt{3}} \).