х^2+3ху-у^2+2х-5у=-64
х-у=-7
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x=y - 7
(y-7)^2 + 3y(y-7) - y^2 + 2(y-7) - 5y = -64
y^2 - 14y + 49 + 3y^2 - 21y - y^2 + 2y - 14 - 5y + 64 =0
3y^2 - 38y + 99 = 0
D = 38*38 - 4*3*99 = 256 = 16^2
y12= (38 +- 16)/6 = 9 11/3
y1 = 9 x1=y-7=2
y2 = 11/3 x2=11/3 - 7 = -10/3
ответ (-10/3 11/3)( 2 9)