Solution
= Solution
For $f(x)=x^{-2}$,
$$
\operatorname{pr}^{(3)}V_2(S-x^{-2})
=-2S-x\frac{d}{dx}(x^{-2})
=-2S+2x^{-2},
$$
which vanishes when $S=x^{-2}$. The corresponding expressions for $V_1$ and $V_3$ are nonzero on the equation. \b[Thus $S[u]=x^{-2}$ has the dilation symmetry $V_2=x\partial_x$ among the three listed generators.]