[tex]\it 2x-3y=5\ \Rightarrow\ 2x-5=3y\ \Rightarrow\ 3y=2x-5|_{:3}\ \Rightarrow\ y=\dfrac{2x-5}{3}\ \ \ \ \ (*)\\ \\ \\ x=1\ \stackrel{(*)}{\Longrightarrow}\ y=\dfrac{2-5}{3}=\dfrac{-3}{3}=-1\ \Rightarrow\ (1,\ -1) \in S\\ \\ \\ x=4\ \stackrel{(*)}{\Longrightarrow}\ y=\dfrac{2\cdot4-5}{3}=\dfrac{3}{3}=1\ \Rightarrow\ (4,\ 1) \in S[/tex]
