Решение систем уравнений второй степени

Х + 2y = - 8
X = - 2y - 8
- 3( - 2y - 8 )^2 + 8y^2 = 320
- 3( 4y^2 + 32y + 64 ) + 8y^2 = 320
- 12y^2 - 96y - 192 + 8y^2 = 320
- 4y^2 - 96y - 512 = 0
- 4( y^2 + 24y + 128 ) = 0
D = 576 - 512 = 64 = 8^2
y1 = ( - 24 + 8 ) : 2 = - 8
y2 = ( - 24 - 8 ) : 2 = - 16
X1 = - 2•( - 8 ) - 8 = 16 - 8 = 8
X2 = - 2•( - 16 ) - 8 = 32 - 8 = 24