:: Answers to practise problems for triangular block form

    1. \( c_A(\lambda) = (\lambda + 1)^3 \), factors completely
    2. \( \dim G_{-1}(A) = 3 \), which agrees with the algebraic multiplicity of \(\lambda = -1\) from the characteristic polynomial. This generalized eigenspace is, by itself, a complete set of independent subspaces of \(\mathbb{R}^3\).
    3. \( P = \begin{bmatrix} 3 & 1 & 1 \\ 4 & 0 & 0 \\ 0 & 4 & 0 \end{bmatrix} \)

      \( P^{-1} A P = \begin{bmatrix} -1 & 0 & -1 \\ 0 & -1 & -1 \\ 0 & 0 & -1 \end{bmatrix} \)
    1. \( c_A(\lambda) = (\lambda + 1)^2 (x - 1)^2 \), factors completely
    2. \( \dim G_{-1}(A) = 2 \), which agrees with the algebraic multiplicity of \(\lambda = -1\) from the characteristic polynomial.

      \( \dim G_1(A) = 2 \), which agrees with the algebraic multiplicity of \(\lambda = 1\) from the characteristic polynomial.

      Since these two dimensions add to \(4\), and we know that generalized eigenspaces from different eigenvalues are always independent, these two generalized eigenspace together form a complete set of independent subspaces of \(\mathbb{R}^4\).
    3. \( P = \begin{bmatrix} 1 & 1 & 5 & -1 \\ 0 & 0 & 2 & 1 \\ 0 & 1 & 2 & 0 \\ 1 & 0 & 1 & 0 \end{bmatrix}\)

      \( P^{-1} A P = \begin{bmatrix} -1 & 1 & 0 & 0 \\ 0 & -1 & 0 & 0 \\ 0 & 0 & 1 & 2 \\ 0 & 0 & 0 & 1 \end{bmatrix}\)