Which one of the following matrices does not have an LU decomposition, where L and U are lower and upper triangular matrices respectively?
1
\(M = \left[ {\begin{array}{*{20}{c}} 1&0\\ 0&1 \end{array}} \right]\)
2
\(M = \left[ {\begin{array}{*{20}{c}} 0&1\\ 1&1 \end{array}} \right]\)
3
\(M = \left[ {\begin{array}{*{20}{c}} 1&1\\ 0&1 \end{array}} \right]\)
4
\(M = \left[ {\begin{array}{*{20}{c}} 1&0\\ 1&1 \end{array}} \right]\)