Eigenvectors Transformation
1. **State the problem:** Find the eigenvectors of the matrix $$A = \begin{pmatrix}1 & 1 \\ 3 & -1\end{pmatrix}$$ using the transformation method.
2. **Find the eigenvalues:** Solve the characteristic equation $$\det(A - \lambda I) = 0$$ where $$I$$ is the identity matrix.
$$A - \lambda I = \begin{pmatrix}1 - \lambda & 1 \\ 3 & -1 - \lambda\end{pmatrix}$$
Calculate the determinant:
$$\det(A - \lambda I) = (1 - \lambda)(-1 - \lambda) - 3 \times 1 = (1 - \lambda)(-1 - \lambda) - 3$$
Expand:
$$= -(1 - \lambda)(1 + \lambda) - 3 = -(1 - \lambda^2) - 3 = -1 + \lambda^2 - 3 = \lambda^2 - 4$$
Set equal to zero:
$$\lambda^2 - 4 = 0$$
Solve for $$\lambda$$:
$$\lambda = \pm 2$$
3. **Find eigenvectors for $$\lambda = 2$$:**
Solve $$ (A - 2I)\mathbf{x} = 0 $$
$$A - 2I = \begin{pmatrix}1 - 2 & 1 \\ 3 & -1 - 2\end{pmatrix} = \begin{pmatrix}-1 & 1 \\ 3 & -3\end{pmatrix}$$
Set up the system:
$$-x_1 + x_2 = 0$$
$$3x_1 - 3x_2 = 0$$
From the first equation:
$$x_2 = x_1$$
Eigenvector corresponding to $$\lambda = 2$$ is any scalar multiple of:
$$\mathbf{v}_1 = \begin{pmatrix}1 \\ 1\end{pmatrix}$$
4. **Find eigenvectors for $$\lambda = -2$$:**
Solve $$ (A + 2I)\mathbf{x} = 0 $$
$$A + 2I = \begin{pmatrix}1 + 2 & 1 \\ 3 & -1 + 2\end{pmatrix} = \begin{pmatrix}3 & 1 \\ 3 & 1\end{pmatrix}$$
Set up the system:
$$3x_1 + x_2 = 0$$
$$3x_1 + x_2 = 0$$
From the equation:
$$x_2 = -3x_1$$
Eigenvector corresponding to $$\lambda = -2$$ is any scalar multiple of:
$$\mathbf{v}_2 = \begin{pmatrix}1 \\ -3\end{pmatrix}$$
**Final answer:**
Eigenvalues: $$\lambda_1 = 2$$ with eigenvector $$\mathbf{v}_1 = \begin{pmatrix}1 \\ 1\end{pmatrix}$$
Eigenvalues: $$\lambda_2 = -2$$ with eigenvector $$\mathbf{v}_2 = \begin{pmatrix}1 \\ -3\end{pmatrix}$$