Let the characteristic equation of a matrix (x - α)3 + (x - &bet...
Understanding the Characteristic Equation
The characteristic equation given is λ^2 - λ - 1. To analyze the implications of this equation, we first need to find its roots using the quadratic formula. The roots will help us determine the eigenvalues of the matrix M.
Eigenvalues and Matrix Inversion
The roots of the equation are:
- λ = (1 ± √5) / 2
These eigenvalues indicate whether the matrix M is invertible. A matrix is invertible if and only if zero is not an eigenvalue. Since neither root is zero, M is indeed invertible.
Matrix Inversion Properties
For a matrix M, the inverse can sometimes be expressed in terms of its eigenvalues. In this case, we have the condition that:
- M - I = 0
This expression suggests that the matrix M can be adjusted by subtracting the identity matrix, leading to the conclusion that:
- M - I is a matrix that can yield the identity when manipulated correctly.
Conclusion: Why Option C is Correct
Given the options, we find that:
- Option C states M^(-1) = M - I, which aligns with our understanding that subtracting the identity matrix brings us back to a form that is manageable and consistent with the eigenvalues we derived.
Thus, the correct answer is indeed:
- M^(-1) = M - I
This result highlights the unique relationship between M and its inverse in this specific characteristic equation context.