Find the value of m if 𝑢⃗ = [4, 7, m] and 𝑏⃗ = [m, 6, -2] are perpendicular vectors.

Answer 1

If two vectors are perpendicular, then the dot product is zero so

u^→ . b^→ = 0

(4,7,m).(m,6,-2)=0

4m+42-2m=0

m=21.

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