Find a redundant column vector of the given matrix $A$, and write it as a linear combination of preceding columns. Use this representation to write a nontrivial relation among the columns, and thus find a nonzero vector in the kernel of A. (This procedure is illustrated in Example $8 .$)
$$\left[\begin{array}{ll}
0 & 1 \\
0 & 2
\end{array}\right]$$