The eigen values of the matrix $$M$$ given are $$15, 3, $$ and $$0.$$
$$M = \left[ {\matrix{ 8 & { - 6} & 2 \cr { - 6} & 7 & { - 4} \cr 2 & { - 4} & 3 \cr } } \right],$$ the value of the determinant of a matrix is

The value of the following determinant $$\left[ {\matrix{ 1 & 4 & 9 \cr 4 & 9 & {16} \cr 9 & {16} & {25} \cr } } \right]$$ is

The matrix $$\left[ {\matrix{ 1 & { - 4} \cr 1 & { - 5} \cr } } \right]$$ is an inverse of the matrix $$\left[ {\matrix{ 5 & { - 4} \cr 1 & { - 1} \cr } } \right]$$

For the following matrix $$\left[ {\matrix{ 1 & { - 1} \cr 2 & 3 \cr } } \right]$$ the number of positive characteristic roots is