Решите систему уравнений методом подстановки: а)х+у=1, ху=-1     б)х^+ху=6, х-у=4

а){х+у=1{ху=-1     {x = 1 - y{xy  =-1{x = 1 - y{y(1 - y) = -1{x = 1 - y{y^2 - y - 1 = 0{x = 1 - y{y^2  - y - 1 = 0D = 1 + 4 = 5y1 = 1 + √5 => x1 = -√5y2 = 1 - √ 5 => x2 = √5б){х^2+ху=6{х-у=4{x^2 + xy = 6{y = x - 4{x^2 + x(x-4) = 6{y = x - 4{y = x - 4{2x^2 - 4x - 6 = 0{y = x - 4{x^2 - 2x  -3 = 0D/4 = 1 + 3 = 4x1 = 1 + 2= 3 => y1 = -1x2 = 1- 2 = -1 => y2 = -5