[m]y^2-xy-5y+x+4=0 ⇔ \left[ \begin{gathered} y-1=0 \\ y-4-x=0 \end{gathered} \right.[/m]
Система
[m]\left\{\begin {matrix}\frac{(y^2-xy-5y+x+4)\sqrt{x+2}}{\sqrt{4-y}}=0\\a=x+y-2\end {matrix}\right.[/m]
равносильна системе
[m]\left\{\begin {matrix}\left[ \begin{gathered} y-1=0 \\ y-4-x=0\\x+2=0 \end{gathered} \right.\\ x+2 ≥ 0\\4-y>0\\a=x+y-2\end {matrix}\right.[/m]
График первого уравнения системы на рис.
О т в е т. a ∈ [-2; 2) U (2;+ ∞ )