Tìm x, y biết:
a, 2x^2 - 8x + y^2 + 2y + 9 = 0
b, x^2 + y^2 + x - xy + 1/2 = 0
c, x^2 - 4xy + 9y^2 + 9 = 2xy + 6x - x^2
d, 5x^2 + 5y^2 + 8xy + 2y - 2x + 2 = 0
e, 4x^2 + 13y^2 +12xy + 4x - 2y + 5 =0
f, x^2 + 2y^2 - 2xy + 2x + 2 - 4y = 0
g, 8x^3 + (x + 8)^2 = 8(x + 2)(x^2 - 2x + 4)
h, (3x...