3x^2+5xy-4y^2= -25x^2+9xy-2y^2=0
решаем второе уравнение относительно икс
5x^2+9y*x -2y^2=0
D=b^2-4ac=81y^2+4*5*2y^2=81y^2+40y^2=121y^2
x12=(-9y+-11y)/10 = -2y 1/5y
x=-2y
3(-2y)^2 + 5(-2y)y - 4y^2 = 12y^2 - 10y^2-4y^2 = -2y^2
-2y^2=-2
y^2=1
y=1 x=-2
y=-1 x=2
x=1/5y
3(1/5y)^2 + 5 (1/5y)y - 4y^2 = 3/25y^2 + y^2 -4y^2 = 3/25y^2 - 3y^2 = -72/25y^2
-72/25y^2=-2
y^2=25/36
y=5/6 x=1/6
y=-5/6 x=-1/6
ответ (-1/6 -5/6) (1/6 5/6) (-2 1) (2 -1)