Find formulas for the entries of M^n

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Therefore, by using the formula for diagonal matrices, we can write M^n as \tilde{M}^n = \begin{bmatrix} \lambda_1^n & 0 \\ 0 & \lambda_2^n \end{bmatrix} , where \lambda_1 and \lambda_2 are the eigenvalues of M. Therefore, the formulas for the entries of M^n are given by the formula: \begin{align} (M^n)_{11} = d_{11} \lambda_1^n d_{11}^{-1} + d_{12} \lambda_2^n d_{21}^{-1} \\ (M^n)_{12} = d_{11} \lambda
  • #1
icefall5
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Homework Statement


Let [itex]M = \begin {bmatrix} 8 & -1 \\ 2 & 11 \\ \end{bmatrix}[/itex]

Find formulas for the entries of [itex]M^n[/itex], where n is a positive integer.

Homework Equations


N/A

The Attempt at a Solution


I honestly have no clue where to start. We recently covered diagonalization, but I can't see how this relates.
 
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  • #2
Let's suppose D is the transform that diagonalizes M, and denote [itex] D M D^{-1} = \tilde{M} [/itex]. Then
[tex] M^n = M M M ... M = D^{-1} D M D^{-1} D M D^{-1} D M ... M D^{-1} D = D^{-1} \tilde{M}^n D. [/tex]
 
  • #3
clamtrox said:
Let's suppose D is the transform that diagonalizes M, and denote [itex] D M D^{-1} = \tilde{M} [/itex]. Then
[tex] M^n = M M M ... M = D^{-1} D M D^{-1} D M D^{-1} D M ... M D^{-1} D = D^{-1} \tilde{M}^n D. [/tex]
Also, The diagonal entries in [itex]\tilde{M}[/itex] are the eigenvalues of the matrix M and the columns of D are the corresponding eigenvectors of M.
 

FAQ: Find formulas for the entries of M^n

What is the purpose of finding formulas for the entries of M^n?

The purpose of finding formulas for the entries of M^n is to efficiently calculate the nth power of a given matrix M. This can be useful in various mathematical and scientific applications, such as solving systems of linear equations or modeling dynamic systems.

What is the formula for finding the entries of M^n?

The formula for finding the entries of M^n is M^n = PDP^-1, where P is the matrix of eigenvectors of M and D is the diagonal matrix of eigenvalues raised to the nth power.

What are the limitations of using the formula for finding the entries of M^n?

The formula for finding the entries of M^n only applies to square matrices with distinct eigenvalues. It also requires the matrix to be diagonalizable, which is not always the case. Additionally, the formula can become computationally expensive for large values of n.

Can the formula for finding the entries of M^n be used for non-integer values of n?

No, the formula for finding the entries of M^n only applies to integer values of n. For non-integer values, a different approach, such as using Taylor series, may be required.

Are there any alternative methods for finding the entries of M^n?

Yes, there are alternative methods for finding the entries of M^n, such as using the Cayley-Hamilton theorem or the power method. These methods may be more efficient for certain types of matrices or for large values of n.

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