1 [?]. 100-Inch [?]. 10th [?, ?, ?]. 11th [?, ?]. 12-Inch [?, ?, ?, ?]. 121-Mile [?]. 12th [?, ?, ?, ?, ?, ?, ?, ?, ?]. 13-Gun [?]. 13th [?, ?]. 14-inch [?, ?]. 14th [?, ?, ?, ?, ?, ?]. 15th [?, ?, ?, ?]. 16-Inch [?, ?, ?, ?]. 16th [?, ?, ?]. 17-Year [?]. 17th [?, ?, ?, ?]. 18th [?, ?, ?]. 1910 [?, ?, ?]. 1911 [?, ?]. 1913 [?]. 1914 [?]. 1915 [?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ...

We show that a pair of matrices satisfying a certain algebraic identity, reminiscent of the binomial theorem, must have the same characteristic polynomial. This is a generalization of Problem 4 (11th grade) from the Romanian National Mathematical Olympiad 2011.