Find all values of $x$ where the graph of $f(x)=\left(-4 x^{2}+x\right) e^{-4 x}$ has an inflection point.

Step 1 ：Find the second derivative of the function \( f(x) = (-4x^2 + x)e^{-4x} \)

Step 2 ：Set the second derivative equal to zero and solve for \( x \)

Step 3 ：The inflection points are \( x = \frac{1}{4} \) and \( x = 1 \)

Step 4 ：Final Answer: \( \boxed{\frac{1}{4}, 1} \)