Х-у=7 х^2 + у^2 = 9 - 2ху

  Х -  Y = 7  X = Y + 7  X^2 = ( Y + 7)^2 = Y^2 + 14Y + 49  ----------------------------------------- X^2 + Y^2 = 9 - 2XY  Y^2 + 14Y + 49 + Y^2 = 9 - 2Y*( Y + 7)  2Y^2 + 14Y + 49 = 9 - 2Y^2 - 14Y  2Y^2 + 2Y^2 + 14Y + 14Y + 49 - 9 = 0  4Y^2 + 28Y + 40 = 0  -------------------------------------------- D = 784 - 640 = 144 ; V D = 12  Y1 = ( - 28 + 12 ) : 8 = ( - 16 ) : 8 = ( - 2 )  Y2 = ( - 40 ) : 8 = ( - 5 )  -------------------------------------------- X = Y + 7  X1 = - 2 + 7 = 5  X2 = - 5 + 7 = 2  -------------------------------------------  Ответ: ( 5 ; - 2 ) ; ( 2 ; - 5 )