Question

Which of the following is a lower triangular matrix

• A. $\left[\begin{array}{ccc}5& 0& 0\\ 3.5& 1& 0\\ -7& 6& 3\end{array}\right]$
• B. $\left[\begin{array}{ccc}-1& 0.4& 1.7\\ 0& 5& -8\\ 3& 0& -1.8\end{array}\right]$
• C. $\left[\begin{array}{ccc}5& 3& 2\\ 9& 4& 11\\ 2& -23& -7\end{array}\right]$
• D. $\left[\begin{array}{ccc}5& 3& 2\\ 0& -5& 2.6\\ 0& 0& 5\end{array}\right]$

Answer 1

The correct option is A $\left[\begin{array}{ccc}5& 0& 0\\ 3.5& 1& 0\\ -7& 6& 3\end{array}\right]$

A lower triangular matrix is one where all entries above the main diagonal are zero.