152 CHAPTER 8. MATRICES
a computation in matlab, you ought to go to >> and type “clear all” and then enter. Thatway, you can use the symbols again with different definition. If you don’t do the “clear all”thing, it will go on thinking that A is what you defined earlier.
8.8 Exercises1. Here are some matrices:
A =
(1 2 32 1 7
),B =
(3 −1 2−3 2 1
),
C =
(1 23 1
),D =
(−1 22 −3
),E =
(23
).
Find if possible −3A,3B−A,AC,CB,AE,EA. If it is not possible explain why.
2. Here are some matrices:
A =
1 23 21 −1
,B =
(2 −5 2−3 2 1
),
C =
(1 25 0
),D =
(−1 14 −3
),E =
(13
).
Find if possible −3A,3B−A,AC,CA,AE,EA,BE,DE. If it is not possible explainwhy.
3. Here are some matrices:
A =
1 23 21 −1
,B =
(2 −5 2−3 2 1
),
C =
(1 25 0
),D =
(−1 14 −3
),E =
(13
).
Find if possible −3AT ,3B− AT ,AC,CA,AE,ET B,BE,DE,EET ,ET E. If it is notpossible explain why.
4. Here are some matrices:
A =
1 23 21 −1
,B =
(2 −5 2−3 2 1
),
C =
(1 25 0
),D =
(−14
),E =
(13
).
Find the following if possible and explain why it is not possible if this is the case.
AD,DA,DT B,DT BE,ET D,DET .