х^2-ху-у^2=19

х-у=3

x = 3 + y

(3 + y)^2 -(3 + y)y + y^2 = 19

9 + 6y + y^2 - 3y -y^2 + y^2 = 19

x = 3 + y

y^2 + 3y - 10 = 0

y= 5

y= -2

x= 8

x= 1