page 352, Chapter D,

3. Compute the determinant of the matrix

\[ \begin{pmatrix} 3 & 9 & -2 & 4 & 2\\ 0 & 1 & 4 & -2 & 7\\ 0 & 0 & -2 & 5 & 2\\ 0 & 0 & 0 & -1 & 6\\ 0 & 0 & 0 & 0 & 4\\ \end{pmatrix} \] By hand determinant computation

Using R’s det() function to confirm the by hand computation.

x = matrix(c(3,9,-2,4,2,
             0,1,4,-2,7,
             0,0,-2,5,2,
             0,0,0,-1,6,
             0,0,0,0,4), 5, 5)

det(x)
## [1] 24