exo7 4925

$x^2 + y^2 + z^2 -2xy + 2xz + 3x - y + z + 1 = 0$.

$(x-y)(y-z) + (y-z)(z-x) + (z-x)(x-y) + (x-y) = 0$.

$x^2 + 9y^2 + 4z^2 - 6xy - 12yz + 4zx + 4 = 0$.

$x^2 - 2y^2 - z^2 + 2xz - 4yz + 3 = 0$.

$2x^2 + 2y^2 + z^2 + 2xz - 2yz + 4x - 2y - z + 3 = 0$.

$xy + xz + yz + 1 = 0$.

$2x^2 + 2y^2 - z^2 + 5xy - yz + xz = 0$.

$xy + yz = 1$.

$x^2 + 4y^2 + 5z^2 - 4xy - 2x + 4y = 0$.

On fera le minimum de calculs nécéssaires pour pouvoir conclure.