Answer
See below.
Work Step by Step
We know that if a matrix's determinant is $0$, then it is singular.
We know that for a matrix
\[
\left[\begin{array}{rr}
a & b \\
c &d \\
\end{array} \right]
\]
the determinant, $D=ad-bc.$
Hence here $D=4\cdot2-(-8)\cdot(-1)=8-8=0.$ Thus the matrix is singular.
