Решите систему уравнений 1)х^2 + 10ху +25у^2= 9 2) х-5у=7

{ x² + 10xy + 25y² = 9
{ x - 5y = 7

{ (x + 5y)² = 9
{ x = 5y + 7

(5y + 7 + 5y)² = 9
(10y + 7)² = 3²
10y + 7 = 3                  10y + 7 = -3        
 y = -0,4                          y = -1                   
 x = 5                              x = 2                   

ответ: {5; -0,4}, {2; -1}