⑴a+b =； ⑵a-b =；

⑶λa =； ⑷ a b=

How to prove the above algorithm? (Just substitute A = I+J+K and B = I+J+K)

2. How to find the coordinates of a space vector? (The coordinates representing the end of the directed line segment of this vector minus the coordinates of the starting point. )

3. Exercise: (1) The coordinate of a vector parallel to the vector (1,-3,2) is (c).

A.( 1，3，2) B.(- 1，-3，2) C.(-2，6，-4) D.( 1，-3，-2)

(2) Given point A (1, 2,-1), vector OC and vector OA are symmetric about plane xoy, and vector OB and vector OA are symmetric about plane X, find the vector sum.

Answer: = (0,4,0) = (0,4,2)

(3) Known vector =(2,-1, 3) Find a vector so that ∨ and ∣ ∣ = 3 ∣.

Answer: =(6,-3,9) or = (-6,3,5)

(4) Given three points A (- 1, 0,2), B (- 1, 1, 2) and C (-3,0,4), let =, =,

If K+ and k -2 are perpendicular to each other, find the value of k. (K=2 or k =-)