A First Course in Linear Algebra · Problem T15

Eigenvalues — Robert Beezer

Mathematics — Linear Algebra · characteristic-polynomial-alternate-definition

Problem

The characteristic polynomial of the square matrix AA is usually defined as rA(x)=det⁡(xIn−A)r_A(x) = \det(xI_n - A). Find a specific relationship between our characteristic polynomial, pA(x)p_A(x), and rA(x)r_A(x), give a proof of your relationship, and use this to explain why Theorem EMRCP can remain essentially unchanged with either definition. Explain the advantages of each definition over the other. (Computing with both definitions, for a 2×22 \times 2 and a 3×33 \times 3 matrix, might be a good way to start.)

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