$\left[ {\begin{array}{*{20}{c}}
1&a&b\\
c&1&d\\
e&f&1
\end{array}} \right]$
where exactly one of $a, b, c, d, e, f$ is $1$ and rest of them are zeros, is invertible. There are six such matrices.
Also, the matrix $\left[\begin{array}{lll}{1} & {0} & {1} \\ {0} & {1} & {0} \\ {1} & {0} & {0}\end{array}\right]$ is invertible.
Thus, there are at least $7$ such matrices which are invertible.
$x+y+3 z=0$
$x+3 y+k^{2} z=0$
$3 x+y+3 z=0$
માટે શૂન્યેતર ઉકેલ $(x, y, z)$ જ્યાં $k \in R$ હોય તો $x +\left(\frac{ y }{ z }\right)$ ની કિમત મેળવો