identify the following equations

[tex]x + y = 1[/tex]
[tex] {x}^{2} + {y}^{2} = 1[/tex]
[tex] {x}^{2} - {y}^{2} = 1[/tex]
[tex]2 {x}^{2} + {y}^{2} = 1[/tex]
[tex] {x}^{2} + {y}^{} + 3 = 0[/tex]