For v=4i-8j, find unit vector u in the direction of v a. u= 1/3i - 2/3j b. i-j c. sqrt3/3 i - 2 sqrt3/3 j d. sqrt5/5 i - 2 sqrt5/5 j

The unit vector is given by:
 u = v / lvl
 The module of v is:
 lvl = root ((4) ^ 2 + (-8) ^ 2)
 lvl = root (16 + 64)
 lvl = root (80)
 lvl = 4 * root (5)
 Substituting:
 u = 4i-8j / (4 * root (5))
 Rewriting:
 u = i-2j / root (5)
 u = root (5) / 5 i - 2 * root (5) / 5 j
 
 The unit vector in the direction of v is:
 d. sqrt5 / 5 i - 2 sqrt5 / 5 j