Sur l'épreuve Mines et Ponts 2013 MP Math 1

A problem that must have baffled more than one person. We want to solve an equation where the unknown is a symmetric bilinear map, and the goal is to show that the solutions of this equation are diagonalizable. But on closer inspection, we're studying bilinear maps, not bilinear forms... Strange, isn't it? In a future video, we'll put this problem back into its true context: curvature tensors on Riemannian manifolds!