Answer
$-4$, invertible
Work Step by Step
We know that for a matrix
$
\left[\begin{array}{rrr}
a & b & c \\
d &e & f \\
g &h & i \\
\end{array} \right]
$
the determinant is given as:
$D=a(ei-fh)-b(di-fg)+c(dh-eg).$
Thus, we have:
$D=-2(4\cdot1-0\cdot2)-(-1.5)(2\cdot1-0\cdot0.5)+0.5(2\cdot2-4\cdot0.5)=-2(4)+1.5(2)+0.5(2)=-4.$
The determinant is not $0$, so the matrix is invertible.
