\({\overrightarrow {\text{p}} _x} + {\overrightarrow {\text{p}} _y} = {\overrightarrow {\text{p}} _{{\text{final}}}}\)

\(\mathrm{m}_{\mathrm{x}} \mathrm{V}_{\mathrm{x}}-\mathrm{m}_{\mathrm{y}} \mathrm{V}_{\mathrm{y}}=\left(\mathrm{m}_{\mathrm{x}}+\mathrm{m}_{\mathrm{y}}\right) \mathrm{V}\)

\(\frac{\mathrm{h}}{\lambda_{\mathrm{x}}}-\frac{\mathrm{h}}{\lambda_{\mathrm{y}}}=\frac{\mathrm{h}}{\lambda}\)

\(\Rightarrow \lambda=\frac{\lambda_{x} \lambda_{y}}{\left|\lambda_{x}-\lambda_{y}\right|}\)