Question

Find the value of a for which the vector 3i+3j+9k and I+aj+3k are parallel

Answer 1

Answer:

$\frac{-29}{3}$

Explanation:

Two vectors are perpendicular if their dot product is zero, and parallel if their dot product is 1.

so multiply them

multiply i with i

j with j and k with k

we get 3+3a+27=1

a = $\frac{-29}{3}$