For this case we have the following vector:
v = (- 8, 2)
Using product point we have:
v.v = (-8, 2). (- 8, 2)
v ^ 2 = (-8) * (- 8) + (2) * (2)
v ^ 2 = 64 + 4
v ^ 2 = 68
v = root (68)
v = root (4 * 17)
v = 2 * root (17)
Answer:
v = 2 * root (17)
option c