find a unit vector in the direction of u

Question

u = (-5, -12, 9)

a. (-5, -12, 9)
b. 1 / squareroot 26 (-5, -12, 9)
c. squareroot 26 (-5, -12, 9
d. 1/ 5 squareroot 10 (-5, -12, 9)
e. 1/ 5 squareroot 10 (5, 12, -9)

Answer 1

5^2 + 12^2 + 9^2 = 250
length = sqrt 250 = 5 sqrt 10

so
(1 / 5sqrt10) (-5,-12,9)