If 4i+j-k and 3i+mj+2k are at right angle, then m = - Vidyadip

MCQ

If $4i+j-k$ and $3i+mj+2k$ are at right angle, then $m = $

A
$-6$
B
$-8$
✓
$-10$
D
$-12$

✓

Answer

Correct option: C.

$-10$

c
(c) Since angle between the vectors is ${90^o}$, therefore dot product of the vectors will be zero

or $(4i + j - k)\,.\,(3i + mj + 2k) = 0$

or $12 + m - 2 = 0$ or $m = - 10.$

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