Diketahuivektor-vektora ⃗=2i ⃗+4j ⃗+k ⃗, b ⃗=-3i ⃗+mj ⃗-2k ⃗ . vektora ⃗ tegak lurus b ⃗ , maka nilai m sama dengan …

a = 2i + 4j + k = (2, 4, 1)
b = -3i + mj - 2k = (-3, m, -2)

tegak lurus maka a . b = 0
(2, 4, 1) × (-3, m, -2) = 0
( (2 × (-3)) + (4 × m) (1 × (-2)) = 0
-6 + 4m - 2 = 0
4m = 8
m = 8 / 4
m = 2

sehingga nilai m = 2