  In this paper, we focus on the partial differential equation
\begin{equation*}
  (-\Delta)^\frac{\alpha}{2} u(x)=f(x,u(x))\;\;\;\;\text{ in }\mathbb{R}^n,
\end{equation*} where $0<\alpha\leq 2$. By the direct method of scaling spheres
investigated by Dai and Qin (\cite{dai2023liouville}, \textit{International
Mathematics Research Notices, 2023}), we derive a Liouville-type theorem. This
mildly extends the previous researches on Liouville-type theorem for the
semi-linear equation $ (-\Delta)^\frac{\alpha}{2} u(x)=f(u(x))$ where the
nonlinearity $f$ depends solely on the solution $u(x)$, and covers the
Liouville-type theorem for Hardy-H\'enon equations $(-\Delta)^\frac{\alpha}{2}
u(x)=|x|^au^p(x)$.
