Question

Determine the value of a so that A = 2i+aj+k and B = 4i-2j-2k are perpendicular​

Answer 1

In order to make them perpendicular, their dot product must result in zero. so:

$4 \times 2 - 2a - 2 \times 1 = 0$

$2a = 8 - 2 = 6$

$a = 3$