Find u × v, v × u, and v × v. u = (9, 2, 1) v = (−4, 8, −2 )?

Answer 1

You have been given correct answers for the first two. As for v × v, the cross product of any 3-dimensional vector with itself returns the zero vector.

|v × v| = |v| |v| sin(θ)

The angle θ is the angle between the two argument vectors. Since the vectors are identical, the angle between them is zero, and sin(0) = 0.

Answer 2

First note that u x v = - v x u so you only have to do the multiplications once.

u x v = i*(-4 - 8) + j*(-4 - (-18)) + k*(72 - (-8))

      = i*(-12) + j*14 + k*80 =(-12, 14,80)

v x u = - u x v = (12, -14, -80)

Answer 3

Just plug in your given values and do the cross multiplication. 

You do know the procedure, right? It's just following the procedure, following the rules. 

If you were not anon I would detail further.