(a) A^2 = -1,A having only real entries.
(b) B^2 = 0,although B不等於0.
(c) C D= - DC , not allowing the case CD=0.
(d) EF =0 ,although no entries of E or F are zero.
2. If A is m by n,how many separate muiltiplications are involved when
(a) A muiltiplies a vector x with n component?
(b) A muiltiplies an n by p matrix B? Then AB is m by p.
(c) A muiltiplies itself to produce A^2? Here m=n.
3. Invent a 3 by 3 matrix M with entries 1,2,...,9. All rows and columns and diagonals add to 15.The first row could be 8,3,4. What times(1,1,1) ?What is the row Vector[ 1 1 1] times M?
更新1:
第一題 (a) A^2 = - I ← 打錯了 是 I 不是1
更新2:
muiltiplies 不小心多打個i 是multiplies
