Answer
$m=\pm 4i$
Work Step by Step
Step 1: $m^{2}-4=-20$
Step 2: $m^{2}=-20+4$
Step 3: $m^{2}=-16$
Step 4: Using the square root property, $m=\pm\sqrt {-16}$.
Step 5: $m=\pm\sqrt {-1\times16}$
Step 6: $m=\pm\sqrt {-1}\times\sqrt {16}$
Step 7: $m=\pm i\times4$
Step 8: $m=\pm 4i$
