An eigenvalue tells you how much a special direction gets stretched or shrunk when a matrix transforms it — these special values unlock deep insight into a matrix's behavior.
1-A 2-A 3-A 4-A | 5 diagonal 6 trace 7 = 7 and 1 8 = Trace 10, Determinant 21 9 = λ = 3 or 7 | 10 = 2 and 2 (repeated)