Evaluate the exponential function $f(x)=5^{2 x}$ when $x=-1$

Step 1 ：The problem is asking to evaluate the function \(f(x)=5^{2 x}\) at \(x=-1\). This means we need to substitute \(x=-1\) into the function and calculate the result.

Step 2 ：Substitute \(x=-1\) into the function: \(f(-1)=5^{2(-1)}\)

Step 3 ：Calculate the result: \(f(-1)=0.04\)

Step 4 ：The final answer is \(\boxed{0.04}\)