Question

Find all real values of a such that the given matrix is not invertible.

Answer 1

Answer:

The answer is "0,3,-3".

Step-by-step explanation:

Let the matrix is not invertible.

then |A|=0

$\left|\begin{array}{ccc}0&9&a\\a&1&7\\0&a&1\end{array}\right|=0$

$-a[9-a^2]=0\\\\a=0\\\\a=\pm 3\\\\a=0, 3,-3$