GATE EC 2006 Set 1 Q21 — Linear Algebra

The eigenvalues and the corresponding eigen vectors of a $2 \times 2$ matrix are given by

$$\begin{array}{cc} \textbf{Eigenvalue}& \textbf{Eigenvector} \\ \lambda_1=8 & \text{v}_{1} = \left[ \begin{array} {} 1 \\ 1 \end{array} \right] \\ \lambda_2=4 & \text{v}_{2} = \left[ \begin{array} {c} 1 \\ – 1 \end{array} \right] \end{array}$$

The matrix is