Question Details

Consider an n×n matrix A and a non-zero n×1 vector p. Their product Ap = α² p, where {α ∈ R ∉and α -1,0,1} . Based on the given information, the Eigen value of A² is :

Options

A

α

B

α²

C

√α

D

α4

Correct Answer :

α4

Solution :

The correct option is α4 (which corresponds to Option 4, represented as "α4").

Here is the step-by-step educational explanation of why this option is correct:

1. Understanding the Definition of Eigenvalues and Eigenvectors:
Recall that for an n×n matrix A and a non-zero n×1 vector p, if there exists a scalar λ such that:
Ap=λp
then λ is an eigenvalue of the matrix A, and p is the corresponding eigenvector.

2. Identifying the Eigenvalue of matrix A:
We are given the relation:
Ap=α2p
Comparing this with the definition Ap=λp, we can directly see that:
λ=α2
is the eigenvalue of matrix A associated with the eigenvector p.

3. Determining the Eigenvalues of a Matrix Power:
A fundamental theorem in linear algebra states that if λ is an eigenvalue of a matrix A associated with an eigenvector p, then for any positive integer k, the matrix Ak has the eigenvalue λk associated with the same eigenvector p.

Let us derive this for the case of A2 (where k=2):
We start by multiplying both sides of our initial equation by A from the left:
A(Ap)=A(α2p)

Using the associativity of matrix multiplication and the linearity property (since α2 is a scalar):
A2p=α2(Ap)

Now, substitute the original expression Ap=α2p back into the right side of the equation:
A2p=α2(α2p)
Simplifying the scalar multiplication:
A2p=α4p

4. Conclusion:
The resulting relation A2p=α4p fits the definition of an eigenvalue equation for the matrix A2. Thus, the eigenvalue of A2 is α4.

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