Re: Matrix Form of Quadratic Equations

*To*: mathgroup at smc.vnet.net*Subject*: [mg114230] Re: Matrix Form of Quadratic Equations*From*: Jean Pellegri <Jean.Pellegri at wanadoo.fr>*Date*: Sun, 28 Nov 2010 06:52:36 -0500 (EST)

In : Reduce[ForAll[{x, y}, {x, y}.{{a, b}, {b, d}}.{x, y} == x^2 + y^2 - 2 x y], {a, b, d}, Reals] Out : a == 1 && b == -1 && d == 1