Exercises

Determinants Cofactors Cramer's Rule Partitioned Matrices Elementary Matrices Inverse Matrices Elimination: A = LU
  1. Without row exchange, use elementary matrices to find LU-factorizations for the following matrices. \[ \mbox{(a)} \quad \begin{bmatrix} -8&-5&-6&5 \\ 3&-6&7&-3 \\ -10&-3&4&2 \\ 5&-5&7&8 \end{bmatrix} ; \qquad \mbox{(b)} \quad \begin{bmatrix} 2&1&-1&0 \\ 4&3&3&1 \\ 8&7&9&5 \\ 6&7&9&8 \end{bmatrix} ; \qquad \mbox{(c)} \quad \]
PLU Factorization
  1. Using row exchange and elementary matrices, find PLU-factorizations for the following matrices.
    1. \[ \mbox{(a)} \quad \begin{bmatrix} -9&8&-3&0 \\ -9&-5&5&1 \\ 6&7&3&5 \\ 6&-2&6&7 \end{bmatrix} , \qquad \mbox{(b)} \quad \begin{bmatrix} 5&2&-5&0 \\ 6&-8&-8&-4 \\ 2&9&-9&2 \\ -1&6&6&-6 \end{bmatrix} \]
    Reflection Givens Rotation Special Matrices