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 = 0 D = 1 + 4 = 5 y1 = 1 + √5 => x1 = -√5 y2 = 1 - √ 5 => x2 = √5 б) {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 = 0 D/4 = 1 + 3 = 4 x1 = 1 + 2= 3 => y1 = -1 x2 = 1- 2 = -1 => y2 = -5