[tex]x - 3y = 15 \\ x = 15 + 3y[/tex]
[tex](15 + 3y) {}^{2} + y {}^{2} = 25[/tex]
[tex]225 + 90y + 9y {}^{2} + y {}^{2} = 25[/tex]
[tex]10y {}^{2} + 90y + 200 = 0[/tex]
[tex]y {}^{2} + 9y + 20 = 0[/tex]
[tex](y + 4)(y + 5) = 0[/tex]
[tex]y = - 4 \: \: \: \: \: \: y = - 5[/tex]
[tex]for \: y= - 4 \\ x = 15 + 3( - 4) = 15 - 12 = 3[/tex]
[tex]for \: y = - 5 \\ x = 15 + 3( - 5) = 15 - 15 = 0[/tex]
