Question

If a vector 2i+3j+8k is perpendicular to the vector 4j-4i+ak then value of a is
A) -1
B)1/2
C)-1/2
D)1

Answer 1

C)-1/2 is the answer

Answer 2

Their dot product will be 0.
2x-4 + 3x4 + 8a = 0
8a = - 4
a = - 1/2