Answer
$$EF=\left[\begin{array}{ll}{0} \end{array}\right].$$
Work Step by Step
Since $$
E=\left[\begin{array}{ll}{4} & {2}\end{array}\right], \quad F=\left[\begin{array}{r}{-1} \\ {2}\end{array}\right]
$$
we have
$$EF= \left[\begin{array}{ll}{4} & {2}\end{array}\right] \left[\begin{array}{r}{-1} \\ {2}\end{array}\right]=\left[\begin{array}{ll}{0} \end{array}\right].$$