For the matrix \[\left[ {\begin{array}{*{20}{c}} 4&2 \\ 2&4 \end{array}} \right]\] the eigen value corresponding to the eigen vector \[\left[ {\begin{array}{*{20}{c}} {101} \\ {101} \end{array}} \right]\] is A. 2 B. 4 C. 6 D. 8

2
4
6
8

The correct answer is $\boxed{4}$.

To find the eigenvalues of a matrix, we can use the following formula:

$$\lambda = \frac{tr(A) – \det(A)}{2}$$

where $tr(A)$ is the trace of $A$ and $\det(A)$ is the determinant of $A$.

In this case, we have:

$$tr(A) = 4 + 4 = 8$$

$$\det(A) = 4^2 – 2 \cdot 4 \cdot 2 = 0$$

Therefore, the eigenvalues of $A$ are $\frac{8 – 0}{2} = 4$.

To find the eigenvector corresponding to the eigenvalue $\lambda = 4$, we can use the following formula:

$$v = \frac{1}{\det(A – \lambda I)}(A – \lambda I)u$$

where $u$ is any non-zero vector.

In this case, we can choose $u = \left[ {\begin{array}{*{20}{c}} {101} \ {101} \end{array}} \right]$.

Therefore, the eigenvector corresponding to the eigenvalue $\lambda = 4$ is $\boxed{\left[ {\begin{array}{*{20}{c}} {101} \ {101} \end{array}} \right]}$.

Here is a brief explanation of each option:

  • Option A: $2$ is not an eigenvalue of $A$.
  • Option B: $4$ is an eigenvalue of $A$.
  • Option C: $6$ is not an eigenvalue of $A$.
  • Option D: $8$ is not an eigenvalue of $A$.
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