a1. (a) det a = 2 (a1) - yr2dpmathssl -...
TRANSCRIPT
Matrices (NON GDC) IB Questionbank Maths SL 22
A1. (a) det A = 2 (A1)
A-1 =
⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
=⎟⎟⎠
⎞⎜⎜⎝
⎛
121
223
24
13
21 A1 N2 2
(b) evidence of multiplying by A–1 (M1)
e.g. X = A–1⎟⎟⎠
⎞⎜⎜⎝
⎛− 2264
, A–1 B
correct working A1
e.g. X = ⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛−⎟⎟
⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
⎟⎟⎠
⎞⎜⎜⎝
⎛−⎟⎟⎠
⎞⎜⎜⎝
⎛281020
21,
2264
121
223
,2264
2143
21
X = ⎟⎟⎠
⎞⎜⎜⎝
⎛14510
A2 N3 4
[6]
Matrices (NON GDC) IB Questionbank Maths SL 23
A2. (a) evidence of considering determinant (M1)
e.g. 3 × –3 – (–2) × x, attempt to find inverse
setting the determinant equal to zero (M1)
e.g. –9 + 2x = 0, 2x = 9
29=x A1 N2 3
(b) METHOD 1
⎟⎟⎠
⎞⎜⎜⎝
⎛ −−+−
=−
3 2 3
2911 xx
A (A1) (A1)
Note: Award A1 for Adet1
, A1 for ⎟⎠⎞⎜⎝
⎛ −−3 2
3 x .
one correct equation from A = A–1 (A1)
e.g. xx
xxxx
=+−−−=
+−=
+−=
+−−
29,3
293,2
292,3
293
attempt to solve the equation (M1)
e.g. –3 = 3(–9 + 2x), –9 + 2x = –1
x = 4 (do not accept x = 4, x = 0) A1 N4 5
METHOD 2
A2 = I (A1)
A2 ⎟⎟⎠
⎞⎜⎜⎝
⎛+−
−=
920029x
x (A1)
one correct equation from A2 = I (A1)
e.g. 9 – 2x =1
attempt to solve the equation (M1)
e.g. 2x = 8
x = 4 A1 N4 5 [8]
Matrices (NON GDC) IB Questionbank Maths SL 24
A3. (a) WP = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
6513
A1A1A1 N3
Note: Award A1 for each correct element.
(b) Note: The first two steps may be done in any order.
subtracting (A1)
e.g. ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
101226
– 2WP
multiplying WP by 2 (A1)
e.g. ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
121026
S = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
− 220
A1 N2
[6]
Matrices (NON GDC) IB Questionbank Maths SL 25
A4. (a) evidence of multiplying (M1) e.g. one correct element
AB = ⎟⎟⎠
⎞⎜⎜⎝
⎛−515
A1A1 N3
(b) METHOD 1
evidence of multiplying by A (on left or right) (M1) e.g. AA–1 X = AB, X = AB
X = ⎟⎟⎠
⎞⎜⎜⎝
⎛−515
(accept x = – 15, y = 5) A1 N2
METHOD 2
attempt to set up a system of equations (M1)
e.g. 5103
,51024
=+−
−=+ yxyx
X = ⎟⎟⎠
⎞⎜⎜⎝
⎛−515
(accept x = – 15, y = 5) A1 N2
[5]
Matrices (NON GDC) IB Questionbank Maths SL 26
A5. (a) correct substitution into the formula for the determinant (A1) e.g. det A = 9ex × e3x – ex × ex
det A = 9e4x – e2x A1 N2
(b) recognizing that no inverse implies det A = 0 R1 e.g. 9e4x – e2x = 0, ad – bc = 0
attempt to solve equation (M1)
e.g. e2x = 91
, e–2x = 9, e2x(9e2x – 1) = 0, 9e4x = e2x
rearranging to get correct log equation
e.g. 2x = )eln()e9ln(,9ln2,91ln 24 xxx ==− (A1)
isolating x A1
e.g. x 9,21,
31ln,9ln
21,
91ln
21 =−==−= baxx
x = –ln 3 (accept a = –1, b = 3) A1 N3 [7]
Matrices (NON GDC) IB Questionbank Maths SL 27
A6. (a) (i) AB = ⎟⎟⎠
⎞⎜⎜⎝
⎛4004
(= 4I) A2 N2
(ii) A–1 = ⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
−
−⎟⎟⎠
⎞⎜⎜⎝
⎛−
−
45
23
41
21
,41,
5612
41 B A1 N1
(b) METHOD 1
⎟⎟⎠
⎞⎜⎜⎝
⎛yx
= A–1 C (M1)
=
⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
⎟⎟⎠
⎞⎜⎜⎝
⎛−⎟⎟
⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
−
−⎟⎟⎠
⎞⎜⎜⎝
⎛−⎟⎟⎠
⎞⎜⎜⎝
⎛−
−48
45
23
41
21
48
5612
41 A1
⎟⎟⎠
⎞⎜⎜⎝
⎛−
=⎟⎟⎠
⎞⎜⎜⎝
⎛175
yx
A1A1 N3
METHOD 2
5x + y = 8, 6x + 2y = –4 A1 for work towards solving their system (M1)
⎟⎟⎠
⎞⎜⎜⎝
⎛−
=⎟⎟⎠
⎞⎜⎜⎝
⎛175
yx
A1A1 N3
[7]
Matrices (NON GDC) IB Questionbank Maths SL 28
A7. (a) METHOD 1
M = (M–1)–1 (M1)
M = ⎟⎟⎠
⎞⎜⎜⎝
⎛− 51
02101
A1A1 N3
METHOD 2
⎟⎟⎠
⎞⎜⎜⎝
⎛=⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛1001
2105
dcba
(M1)
5a + b = 1, 2b = 0, 5c + d = 0, 2d = 1 (A1)
M = ⎟⎟⎠
⎞⎜⎜⎝
⎛− 5.01.0
02.0 A1 N3
(b) METHOD 1
evidence of appropriate approach (M1) e.g. X = M–1B
⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛=⎟⎟⎠
⎞⎜⎜⎝
⎛71
2105
yx
A1
= ⎟⎟⎠
⎞⎜⎜⎝
⎛155
A1 N2
METHOD 2
evidence of appropriate approach (M1)
e.g. ⎟⎟⎠
⎞⎜⎜⎝
⎛=⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛− 7
15.01.002.0
yx
0.2x = 1, –0.1x + 0.5y = 7 A1
⎟⎟⎠
⎞⎜⎜⎝
⎛=⎟⎟⎠
⎞⎜⎜⎝
⎛155
yx
A1 N2
[6]
Matrices (NON GDC) IB Questionbank Maths SL 29
A8. (a) evidence of addition (M1) e.g. at least two correct elements
A + B = ⎟⎟⎠
⎞⎜⎜⎝
⎛0124
A1 N2
(b) evidence of multiplication (M1) e.g. at least two correct elements
−3A = ⎟⎟⎠
⎞⎜⎜⎝
⎛−
−−3963
A1 N2
(c) evidence of matrix multiplication (in correct order) (M1)
e.g. AB = ( ) ( ) ( ) ( )
( ) ( )( ) ( ) ( )( )⎟⎟⎠⎞
⎜⎜⎝
⎛−+−−++−+
1103213312012231
AB = ⎟⎟⎠
⎞⎜⎜⎝
⎛−
−11121
A2 N3
[7]
Matrices (NON GDC) IB Questionbank Maths SL 30
A9. (a) det M = − 4 A1 N1
(b) M−1 = ⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
−=⎟⎟⎠
⎞⎜⎜⎝
⎛−
−−−
21
21
41
41
2211
41 A1A1 N2
Note: Award A1 for 41− and A1 for the correct
matrix.
(c) X = M−1 ⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛−
−−−=⎟⎟⎠
⎞⎜⎜⎝
⎛84
2211
41
84
X M1
X = ( )2,323
−==⎟⎟⎠
⎞⎜⎜⎝
⎛−
yx A1A1 N0
Note: Award no marks for an algebraic solution of the system 2x + y = 4, 2x − y = 8.
[6]
Matrices (NON GDC) IB Questionbank Maths SL 31
A10. (a) evidence of correct method (M1) e.g. at least 1 correct element (must be in a 2 × 2 matrix)
AB = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
++−
−−
236
022ppq
q A1 N2
(b) METHOD 1
evidence of using AB = I (M1) 2 correct equations A1A1
e.g. –2 – 2q = 1 and 3 + 2p
= 1, –6 + pq = 0
p = –4, q = 23− A1A1 N1N1
METHOD 2
finding A–1 = ⎟⎟⎠
⎞⎜⎜⎝
⎛−+ 13
26
1 pp
A1
evidence of using A–1 = B (M2)
e.g. qpp
pqpp
=+
−=+
=+
−=+ 6
3– and 26
,6
3 and 16
2
p = –4, q = 23− A1A1 N1N1
[7]
Matrices (NON GDC) IB Questionbank Maths SL 32
A11. (a) Attempt to multiply e.g. ⎟⎟⎠
⎞⎜⎜⎝
⎛++−−+90006201
(M1)
A2 = ⎟⎟⎠
⎞⎜⎜⎝
⎛ −9081
A1 N2
(b) 3X + ⎟⎟⎠
⎞⎜⎜⎝
⎛−=⎟⎟⎠
⎞⎜⎜⎝
⎛ −1243
3021
(M1)
3X = ⎟⎟⎠
⎞⎜⎜⎝
⎛−
−2264
(A1)
X = ⎟⎟⎠
⎞⎜⎜⎝
⎛−
−2264
31
A1 N2
[5]
Matrices (NON GDC) IB Questionbank Maths SL 33
A12. ⎟⎟⎠
⎞⎜⎜⎝
⎛=⎟⎟⎠
⎞⎜⎜⎝
⎛+⎟⎟⎠
⎞⎜⎜⎝
⎛−
−−⎟⎟⎠
⎞⎜⎜⎝
⎛−
−⎟⎟⎠
⎞⎜⎜⎝
⎛−
−0000
1001
4312
64312
4312
k (A1)
M2 = ⎟⎟⎠
⎞⎜⎜⎝
⎛−
−191867
A2
6M = ⎟⎟⎠
⎞⎜⎜⎝
⎛−
−2418612
A1
⎟⎟⎠
⎞⎜⎜⎝
⎛=⎟⎟⎠
⎞⎜⎜⎝
⎛+⎟⎟⎠
⎞⎜⎜⎝
⎛−
−0000
00
5005
kk
A1
k = 5 A1 N2 [6]
Matrices (NON GDC) IB Questionbank Maths SL 34
A13. (a) det A = 5 (A1)
A–1 = ⎟⎟⎠
⎞⎜⎜⎝
⎛−
−7283
51
A1 N2
(b) Set up matrix equation ⎟⎟⎠
⎞⎜⎜⎝
⎛=⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛11
3287yx
(M1)
premultiplying by A–1 M1
A–1⎟⎟⎠
⎞⎜⎜⎝
⎛=⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛ −
11
3287 1Ayx
⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛−=⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛−=⎟⎟⎠
⎞⎜⎜⎝
⎛11
55
51
yx
yx
A1
x = –1, y = 1 A1 N0 [6]
Matrices (NON GDC) IB Questionbank Maths SL 35
A14. (a) (i) a = 5 A1 N1
(ii) b + 9 = 4 (M1)
b = −5 A1 N2
(b) Comparing elements 3(2) − 5(q) = −9 M1
q = 3 A2 N2 [6]
Matrices (NON GDC) IB Questionbank Maths SL 36
A15. (a) ⎟⎟⎠
⎞⎜⎜⎝
⎛=
8246
2k
A (A1)
⎟⎟⎠
⎞⎜⎜⎝
⎛−
=−51224
2k
BA A2 N3
(b) Evidence of using the definition of determinant (M1) Correct substitution (A1) eg 4(5) − 2(2k − 1), 20 − 2(2k − 1), 20 − 4k + 2 det (2A − B) = 22 − 4k A1 N3
[6]
Matrices (NON GDC) IB Questionbank Maths SL 37
A16. (a) A + B = ⎟⎟⎠
⎞⎜⎜⎝
⎛+⎟⎟⎠
⎞⎜⎜⎝
⎛ed
bca 01
0
= ⎟⎟⎠
⎞⎜⎜⎝
⎛++
eb
dca 1
A2 2
(b) AB = ⎟⎟⎠
⎞⎜⎜⎝
⎛+⎟⎟⎠
⎞⎜⎜⎝
⎛ed
bca 01
0 A1A1A1A1 4
Note: Award N2 for finding BA = ⎟⎟⎠
⎞⎜⎜⎝
⎛+ bd
bcead
a.
[6]
Matrices (NON GDC) IB Questionbank Maths SL 38
A17. (a) 4 8 5 2
32 14 1 a−⎛ ⎞ ⎛ ⎞
= −⎜ ⎟ ⎜ ⎟−⎝ ⎠ ⎝ ⎠Q (A1)
9 63
3 14 a−⎛ ⎞
= ⎜ ⎟−⎝ ⎠Q (A1)
3 21413a
−⎛ ⎞⎜ ⎟= −⎜ ⎟⎜ ⎟⎝ ⎠
Q (A1) (N3) 3
(b) 2 4 5 21 7 1 a−⎛ ⎞ ⎛ ⎞
= ⎜ ⎟ ⎜ ⎟−⎝ ⎠ ⎝ ⎠CD
14 4 42 2 7
aa
− − +⎛ ⎞= ⎜ ⎟− +⎝ ⎠
(A1)(A1)(A1)(A1) (N4) 4
(c) det 5 2a= +D (may be implied) (A1)
1 211 55 2a
a− −⎛ ⎞= ⎜ ⎟+ ⎝ ⎠
D (A1) (N2) 2
[9]
Matrices (NON GDC) IB Questionbank Maths SL 39
A18. ⎟⎟⎠
⎞⎜⎜⎝
⎛65–13
X + ⎟⎟⎠
⎞⎜⎜⎝
⎛1001
X = ⎟⎟⎠
⎞⎜⎜⎝
⎛3–084
⎟⎟⎠
⎞⎜⎜⎝
⎛75–14
X = ⎟⎟⎠
⎞⎜⎜⎝
⎛3–084
(M1)
Pre-multiply by inverse of ⎟⎟⎠
⎞⎜⎜⎝
⎛75–14
(M1)
X = ⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛3–084
451–7
331
(A1)(A1)
Note: Award (A1) for determinant, (A1) for matrix ⎟⎟⎠
⎞⎜⎜⎝
⎛451–7
.
= ⎟⎟⎠
⎞⎜⎜⎝
⎛28205928
331
(A1)(A1)(A1)(A1)
⎟⎠⎞⎜
⎝⎛ ====⇒
3328,
3320,
3359,
3328 dcba
OR
⎟⎟⎠
⎞⎜⎜⎝
⎛65–13
=⎟⎟⎠
⎞⎜⎜⎝
⎛+⎟⎟⎠
⎞⎜⎜⎝
⎛dcba
dcba
⎟⎟⎠
⎞⎜⎜⎝
⎛3–084
(A1)
⎟⎟⎠
⎞⎜⎜⎝
⎛++++dbcadbca65–65–
33+ ⎟⎟⎠
⎞⎜⎜⎝
⎛dcba
= ⎟⎟⎠
⎞⎜⎜⎝
⎛3–084
(A1)
4a + c = 4 –5a + 7c = 0 (A1) 4b + d = 8 –5b + 7d = –3 (A1)
Notes: Award (A1) for each pair of equations. Allow ft from their equations.
a = 3328
, b = 3359
, c = 3320
, d = 3328
(A1)(A1)(A1)(A1)
Note: Award (A0)(A0)(A1)(A1) if the final answers are given as decimals ie 0.848, 1.79, 0.606, 0.848.
[8]
Matrices (NON GDC) IB Questionbank Maths SL 40
A19. 2p2 + 12p = 14 (M1) (A1) p2 + 6p – 7 = 0 (p + 7)(p – 1) = 0 (A1) p = –7 or p = 1 (A1) (C4)
Note: Both answers are required for the final (A1). [4]
Matrices (NON GDC) IB Questionbank Maths SL 41
A20. (a) M2 = ⎟⎟⎠
⎞⎜⎜⎝
⎛−⎟⎟⎠
⎞⎜⎜⎝
⎛− 12
2122 aa
= ⎟⎟⎠
⎞⎜⎜⎝
⎛−
−+5222242
aaa (A1)(A1)(A1)(A1) 4
(b) 2a – 2 = –4 ⇒ a = –1 (A1) Substituting: a2 + 4 = (–1)2 + 4 = 5 (A1) 2
Note: Candidates may solve a2 + 4 = 5 to give a = ±1, and then show that only a = –1 satisfies 2a – 2 = –4.
(c) M = ⎟⎟⎠
⎞⎜⎜⎝
⎛−
−1221
M–1 = – ⎟⎟⎠
⎞⎜⎜⎝
⎛−−−−1221
31 (M1)
= ⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛
31
32
32
31
or 1221
31 (A1)
–x + 2y = –3 2x – y = 3
⇒ ⎟⎟⎠
⎞⎜⎜⎝
⎛−=⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛−
−33
1221
yx
(M1)(M1)
⇒ ⎟⎟⎠
⎞⎜⎜⎝
⎛−⎟⎟⎠
⎞⎜⎜⎝
⎛=⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛−
−⎟⎟⎠
⎞⎜⎜⎝
⎛33
1221
31
32
32
31
31
32
32
31
yx
(A1)
⇒ ⎟⎟⎠
⎞⎜⎜⎝
⎛−
=⎟⎟⎠
⎞⎜⎜⎝
⎛11
yx
(A1) 6
ie x = 1 y = –1
Note: The solution must use matrices. Award no marks for solutions using other methods.
[12]
Matrices (NON GDC) IB Questionbank Maths SL 42
A21. B = (BA)A–1 (M1)
= – ⎟⎟⎠
⎞⎜⎜⎝
⎛−
−⎟⎟⎠
⎞⎜⎜⎝
⎛5220
844211
41 (M1)
= – ⎟⎟⎠
⎞⎜⎜⎝
⎛−−−−4816124
41 (A1)
= ⎟⎟⎠
⎞⎜⎜⎝
⎛12431
(A1)
OR
⎟⎟⎠
⎞⎜⎜⎝
⎛=⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛844211
0225
dcba
(M1)
⇒ ⎭⎬⎫
==+221125
aba
⇒ a = 1, b = 3 (A1)
⎭⎬⎫
==+824425
cdc
⇒ c = 4, d = 12 (A1)
B = ⎟⎟⎠
⎞⎜⎜⎝
⎛12431
(A1) (C4)
Note: Correct solution with inversion (ie AB instead of BA) earns FT marks, (maximum [3 marks]).
[4]
Matrices (GDC OPTIONAL) IB Questionbank Maths SL 1
1. Let A = ⎟⎟⎠
⎞⎜⎜⎝
⎛ −41311 x
and B = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
2
3x .
(a) Find AB.
(b) The matrix C = ⎟⎟⎠
⎞⎜⎜⎝
⎛2820
and 2AB = C. Find the value of x.
(Total 6 marks)
Matrices (GDC OPTIONAL) IB Questionbank Maths SL 2
2. Let A = ⎟⎟⎠
⎞⎜⎜⎝
⎛0220
.
(a) Find
(i) A−1;
(ii) A2. (4)
Let B = ⎟⎟⎠
⎞⎜⎜⎝
⎛q
p02
.
(b) Given that 2A + B = ⎟⎟⎠
⎞⎜⎜⎝
⎛3462
, find the value of p and of q.
(3)
(c) Hence find A−1B. (2)
(d) Let X be a 2 × 2 matrix such that AX = B. Find X. (2)
(Total 11 marks)
Matrices (GDC OPTIONAL) IB Questionbank Maths SL 3
3. Let Sn be the sum of the first n terms of the arithmetic series 2 + 4 + 6 + ….
(a) Find
(i) S4;
(ii) S100. (4)
Let M = ⎟⎟⎠
⎞⎜⎜⎝
⎛1021
.
(b) (i) Find M2.
(ii) Show that M3 = ⎟⎟⎠
⎞⎜⎜⎝
⎛1061
.
(5)
It may now be assumed that Mn = ⎟⎟⎠
⎞⎜⎜⎝
⎛1021 n
, for n ≥ 4. The sum Tn is defined by
Tn = M1 + M2 + M3 + ... + Mn .
(c) (i) Write down M4.
(ii) Find T4. (4)
(d) Using your results from part (a) (ii), find T100. (3)
(Total 16 marks)
Matrices (GDC OPTIONAL) IB Questionbank Maths SL 4
4. Matrices A, B and C are defined by
A = ⎟⎟⎠
⎞⎜⎜⎝
⎛2715
B = ⎟⎟⎠
⎞⎜⎜⎝
⎛− 153
42 C = ⎟⎟⎠
⎞⎜⎜⎝
⎛ −2879
.
Let X be an unknown 2 × 2 matrix satisfying the equation
AX + B = C.
This equation may be solved for X by rewriting it in the form
X = A−1 D.
where D is a 2 × 2 matrix.
(a) Write down A−1. (2)
(b) Find D. (3)
(c) Find X. (2)
(Total 7 marks)
Matrices (GDC OPTIONAL) IB Questionbank Maths SL 5
5. Consider the matrix A = ⎟⎟⎠
⎞⎜⎜⎝
⎛172–5
.
(a) Write down the inverse, A–l. (2)
(b) B, C and X are also 2 × 2 matrices.
(i) Given that XA + B = C, express X in terms of A–1, B and C.
(ii) Given that B = ⎟⎟⎠
⎞⎜⎜⎝
⎛2–576
, and C = ,78–05–⎟⎟⎠
⎞⎜⎜⎝
⎛ find X.
(4) (Total 6 marks)
Matrices (GDC OPTIONAL) IB Questionbank Maths SL 6
A1. (a) Attempting to multiply matrices (M1)
⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛+
+=⎟⎟⎠
⎞⎜⎜⎝
⎛++−+=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
⎟⎟⎠
⎞⎜⎜⎝
⎛ −xx
xx
xx
171
8923
2
3
41311 22
A1A1 N3
(b) Setting up equation M1
eg ⎟⎟⎠
⎞⎜⎜⎝
⎛=⎟⎟⎠
⎞⎜⎜⎝
⎛+
+⎟⎟⎠
⎞⎜⎜⎝
⎛=⎟⎟⎠
⎞⎜⎜⎝
⎛++
⎟⎟⎠
⎞⎜⎜⎝
⎛=⎟⎟⎠
⎞⎜⎜⎝
⎛+
+1410
171,
2820
23422,
2820
1712
222
xx
xx
xx
⎟⎟⎠
⎞⎜⎜⎝
⎛=+=+
=+=+
1417101
2823420 2 2 22
xx
xx (A1)
x = −3 A1 N2 [6]
Matrices (GDC OPTIONAL) IB Questionbank Maths SL 7
A2. (a) (i) A−1 = ⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
021
210
A2 N2
(ii) A2 = ⎟⎟⎠
⎞⎜⎜⎝
⎛4004
A2 N2
(b) ⎟⎟⎠
⎞⎜⎜⎝
⎛=⎟⎟⎠
⎞⎜⎜⎝
⎛+⎟⎟⎠
⎞⎜⎜⎝
⎛3462
02
0440
qp
(M1)
p = 2, q = 3 A1A1 N3
(c) Evidence of attempt to multiply (M1)
eg A−1B = ⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
021
210
⎟⎟⎠
⎞⎜⎜⎝
⎛3022
A−1B = ⎟⎟
⎠
⎞⎜⎜
⎝
⎛
11230
⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
121
210
acceptp
q A1 N2
(d) Evidence of correct approach (M1)
eg X = A−1B, setting up a system of equations
X = ⎟⎟
⎠
⎞⎜⎜
⎝
⎛
11230
⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
121
210
acceptp
q A1 N2
[11]
Matrices (GDC OPTIONAL) IB Questionbank Maths SL 8
A3. (a) (i) S4 = 20 A1 N1
(ii) u1 = 2, d = 2 (A1)
Attempting to use formula for Sn M1
S100 = 10100 A1 N2
(b) (i) M2 = ⎟⎟⎠
⎞⎜⎜⎝
⎛1041
A2 N2
(ii) For writing M3 as M2 × M or M × M2 ⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎟⎠
⎞⎜⎜⎝
⎛1041
1021
or M1
M3 = ⎟⎟⎠
⎞⎜⎜⎝
⎛++++10002401
A2
M3 = ⎟⎟⎠
⎞⎜⎜⎝
⎛1061
AG N0
(c) (i) M4 = ⎟⎟⎠
⎞⎜⎜⎝
⎛1081
A1 N1
(ii) T4 = ⎟⎟⎠
⎞⎜⎜⎝
⎛+⎟⎟⎠
⎞⎜⎜⎝
⎛+⎟⎟⎠
⎞⎜⎜⎝
⎛+⎟⎟⎠
⎞⎜⎜⎝
⎛1081
1061
1041
1021
(M1)
= ⎟⎟⎠
⎞⎜⎜⎝
⎛40204
A1A1 N3
(d) T100 = ⎟⎟⎠
⎞⎜⎜⎝
⎛++⎟⎟⎠
⎞⎜⎜⎝
⎛+⎟⎟⎠
⎞⎜⎜⎝
⎛10
2001...
1041
1021
(M1)
= ⎟⎟⎠
⎞⎜⎜⎝
⎛1000
10100100 A1A1 N3
[16]
Matrices (GDC OPTIONAL) IB Questionbank Maths SL 9
A4. (a) A−1 = ⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
−
−
35
37
31
32
or ⎟⎟⎠
⎞⎜⎜⎝
⎛−−
−⎟⎟⎠
⎞⎜⎜⎝
⎛−
−67.133.2333.0667.0
or5712
31 (A1)(A1) (N2)
(b) AX = C − B (may be implied) (A1)
X = A−1 (C−B) (A1)
D = C − B
= ⎟⎟⎠
⎞⎜⎜⎝
⎛−−1311117
(A1) (N3)
(c) X = ⎟⎟⎠
⎞⎜⎜⎝
⎛ −4231
(A2) (N2)
[7]
Matrices (GDC OPTIONAL) IB Questionbank Maths SL 10
A5. (a) det A = 5(1) – 7(–2) = 19
A–1 = ⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
−=⎟⎟⎠
⎞⎜⎜⎝
⎛−
195
197192
191
5721
191
(A2)
Note: Award (A1) for ⎟⎟⎠
⎞⎜⎜⎝
⎛− 57
21, (A1) for dividing by 19.
OR
A–1 = ⎟⎟⎠
⎞⎜⎜⎝
⎛− 263.0368.0
105.00526.0 (G2) 2
(b) (i) XA + B = C ⇒ XA = C – Β (M1) X = (C – Β)Α–1 (A1)
OR
X = (C – B)A–1 (A2)
(ii) (C – Β)Α–1 = ⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
−⎟⎟⎠
⎞⎜⎜⎝
⎛−
−−
195
197192
191
913711
(A1)
⇒ X = ⎟⎟⎠
⎞⎜⎜⎝
⎛−
−=
⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
−
−
1432
1919
1976
1957
1938
(A1)
OR
X = ⎟⎟⎠
⎞⎜⎜⎝
⎛−
−1432
(G2) 4
Note: If premultiplication by A–1 is used, award (M1)(M0) in
part (i) but award (A2) for ⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛ −
1994
1912
1911
1937
in part (ii).
[6]
Matrices (GDC) IB Questionbank Maths SL 1
1. The system of linear equations below can be written as the matrix equation MX = N.
x + 6y – 3z = –1 4x + 2y – 4z = 12 x + y + 5z = 15
(a) Write down the matrices M and N. (3)
(b) Solve the matrix equation MX = N. (3)
(c) Hence write down the solution of the system of linear equations. (1)
(Total 7 marks)
Matrices (GDC) IB Questionbank Maths SL 2
2. Let A = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−−
−
342411321�and B =
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛−132
.
(a) Write down A–1. (2)
(b) Solve AX = B. (3)
(Total 5 marks)
Matrices (GDC) IB Questionbank Maths SL 3
3. Consider the function f(x) = px3 + qx2 + rx. Part of the graph of f is shown below.
The graph passes through the origin O and the points A(–2, –8), B(1, –2) and C(2, 0).
(a) Find three linear equations in p, q and r. (4)
(b) Hence find the value of p, of q and of r. (3)
(Total 7 marks)
Matrices (GDC) IB Questionbank Maths SL 4
4. Let f(x) = ax2 + bx + c where a, b and c are rational numbers.
(a) The point P(–4, 3) lies on the curve of f. Show that 16a –4b + c = 3. (2)
(b) The points Q(6, 3) and R(–2, –1) also lie on the curve of f. Write down two other linear equations in a, b and c.
(2)
(c) These three equations may be written as a matrix equation in the form AX = B,
where X = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
cba
.
(i) Write down the matrices A and B.
(ii) Write down A–1.
(iii) Hence or otherwise, find f(x). (8)
(d) Write f(x) in the form f(x) = a(x – h)2 + k, where a, h and k are rational numbers. (3)
(Total 15 marks)
Matrices (GDC) IB Questionbank Maths SL 5
5. Let A = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−
124032103
.
(a) Write down A–1. (2)
(b) Let B be a 3 × 3 matrix. Given that AB + ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−−
=⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−
−
571856767
1029435123
, find B.
(4) (Total 6 marks)
Matrices (GDC) IB Questionbank Maths SL 6
6. Let A = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−
−
220112311
.
(a) Write down A–1. (2)
The matrix B satisfies the equation 1
21 −
⎟⎠⎞⎜
⎝⎛ − BI = A, where I is the 3 × 3 identity matrix.
(b) (i) Show that B = –2(A–1 – I).
(ii) Find B.
(iii) Write down det B.
(iv) Hence, explain why B–1 exists. (6)
Let BX = C, where X = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
zyx�and C =
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛−112
.
(c) (i) Find X.
(ii) Write down a system of equations whose solution is represented by X. (5)
(Total 13 marks)
Matrices (GDC) IB Questionbank Maths SL 7
7. (a) Write down the inverse of the matrix A = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−
−
351122131
.
(2)
(b) Hence solve the simultaneous equations
x – 3y + z = 1 2x + 2y – z = 2 x – 5y + 3z = 3
(4) (Total 6 marks)
Matrices (GDC) IB Questionbank Maths SL 8
8. (a) Write down the inverse of the matrix A = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛ −
314102031
.
(b) Hence or otherwise solve
x − 3y = 1
2x + z = 2
4x + y + 3z = −1
(Total 6 marks)
Matrices (GDC) IB Questionbank Maths SL 9
9. Let A = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
102213321
, B = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
132318
and X = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
zyx
.
(a) Write down the inverse matrix A−1.
(b) Consider the equation AX = B.
(i) Express X in terms of A−1 and B.
(ii) Hence, solve for X. (Total 6 marks)
Matrices (GDC) IB Questionbank Maths SL 10
10. The matrix A = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−−122113021
has inverse A−1 = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛ −−−
ba 6113221
.
(a) Write down the value of
(i) a;
(ii) b.
Consider the simultaneous equations
x + 2y = 7
–3x + y – z = 10
2x – 2y + z = –12
(b) Write these equations as a matrix equation.
(c) Solve the matrix equation. (Total 6 marks)
Matrices (GDC) IB Questionbank Maths SL 11
11. The function f is given by f (x) = mx3 + nx2 + px + q, where m, n, p, q are integers. The graph of f passes through the point (0, 0).
(a) Write down the value of q. (1)
The graph of f also passes through the point (3, 18).
(b) Show that 27 m+ 9n + 3p =18.
The graph of f also passes through the points (1, 0) and (–1, –10). (2)
(c) Write down the other two linear equations in m, n and p. (2)
(d) (i) Write down these three equations as a matrix equation.
(ii) Solve this matrix equation. (6)
(e) The function f can also be written f (x) = x (x −1)(rx − s) where r and s are integers. Find r and s.
(3) (Total 14 marks)
Matrices (GDC) IB Questionbank Maths SL 12
12. (a) Write down the inverse of the matrix A = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−
−
351122131
(b) Hence solve the simultaneous equations
x – 3y + z = 1
2x + 2y – z = 2
x – 5y + 3z = 3 (Total 6 marks)
Matrices (GDC) IB Questionbank Maths SL 13
A1. (a) M = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛−=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛−−
15121
,511424361N A2A1 N3 3
(b) evidence of appropriate approach (M2)
e.g. X = M–1N, attempting to solve a system of three equations
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛=205
X A1 N3 3
(c) x = 5, y = 0, z = 2 A1 N1 1 [7]
Matrices (GDC) IB Questionbank Maths SL 14
A2. (a) A–1 =
⎟⎟⎟⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜⎜⎜⎜
⎝
⎛
⎟⎟⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜⎜⎜
⎝
⎛
−
−
−−
=⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−
−−
310
32
311
35
352
313
333.00667.0333.0167.167.1233.4
A2 N2
(b) evidence of attempting to solve equation (M1) e.g. multiply by A–1 (on left or right), setting up system of equations
X = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−
−
101
(accept x = 1, y = 0, z = –1) A2 N3
[5]
Matrices (GDC) IB Questionbank Maths SL 15
A3. (a) attempt to substitute points into the function (M1) e.g. –8 = p(–2)3 + q(–2)2 + r(–2), one correct equation
–8 = –8p + 4q – 2r, –2 = p + q + r, 0 = 8p + 4q + 2r A1A1A1 N4
(b) attempt to solve system (M1) e.g. inverse of a matrix, substitution
p = 1, q = –1, r = –2 A2 N3
Notes: Award A1 for two correct values. If no working shown, award N0 for two correct values.
[7]
Matrices (GDC) IB Questionbank Maths SL 16
A4. (a) evidence of substituting (–4, 3) (M1) correct substitution 3 = a(–4)2 + b(–4) + c A1 16a – 4b + c = 3 AG N0
(b) 3 = 36a + 6b + c, –1 = 4a – 2b + c A1A1 N1N1
(c) (i) A = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−
−
133
;12416361416B A1A1 N1N1
(ii) A–1 =
⎟⎟⎟⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜⎜⎜⎜
⎝
⎛
⎟⎟⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜⎜⎜
⎝
⎛
−
−
−
=⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−
−
23
101
53
81
403
51
161
801
201
5.11.06.0125.0075.02.00625.00125.005.0
A2 N2
(iii) evidence of appropriate method (M1) e.g. X = A–1B, attempting to solve a system of three equations
X = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−35.025.0
(accept fractions) A2
f(x) = 0.25x2 – 0.5x – 3 (accept a = 0.25, b = –0.5, c = –3, or fractions) A1 N2
(d) f(x) = 0.25(x – 1)2 – 3.25 (accept h = 1, k = –3.25, a = 0.25, or fractions) A1A1A1 N3 [15]
Matrices (GDC) IB Questionbank Maths SL 17
A5. (a) A–1 = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−−−
968212323
A2 N2
(b) evidence of subtracting matrices (M1)
e.g. ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−−
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−
−−
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−−
1551012218410
,1029435123
571856767
, D – C
evidence of multiplying on left by A–1 (M1)
e.g. A–1 AB, A–1(D – C), ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−−
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−−−
1551012218410
968212323
B = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛ −
114201312
A2 N3
[6]
Matrices (GDC) IB Questionbank Maths SL 18
A6. (a) A–1 = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−
−−
75.05.0125.15.01111
A2 N2
(b) (i) I – 21
B = A–1 A1
21− B = A–1 – I A1
B = –2(A–1 – I) AG
(ii) B = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−−
−
5.0125.232224
A2 N2
(iii) det B = 12 A1 N1
(iv) det B ≠ 0 R1 N1
(c) (i) evidence of using a valid approach M1 e.g. X = B–1C
X =
⎟⎟⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜⎜⎜
⎝
⎛
⎟⎟⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜⎜⎜
⎝
⎛
=⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
34131
33.11333.0
A1 N1
(ii) 4x – 2y + 2z = 2, –2x + 3y – 2.5z = –1, –2x + y + 0.5z = 1 A1A1A1 N3 [13]
Matrices (GDC) IB Questionbank Maths SL 19
A7. (a) A–1 = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−
8.02.02.13.02.07.01.04.01.0
A2 N2
(b) For recognizing that the equations may be written as A⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
321
zyx
(M1)
for attempting to calculate ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛−
6.16.02.1
321
1Azyx
M1
x = 1.2, y = 0.6, z = 1.6 (accept row or column vectors) A2 N3 [6]
Matrices (GDC) IB Questionbank Maths SL 20
A8. (a) A−1 = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−−−−
2.16.24.02.06.04.06.08.12.0
A2 N2
(b) For recognizing that the equations may be written as A⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
121
zyx
(M1)
For attempting to calculate ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛−
121
A 1
zyx
(M1)
x = 4, y = 1, z = −6 A2 N4 [6]
Matrices (GDC) IB Questionbank Maths SL 21
A9. (a) A−1 = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−−−−
⎟⎟⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜⎜⎜
⎝
⎛
−
−−
−−
1.6733.1667.02.3367.1333.00.3330.667333.0
or
35
34
32
37
35
31
31
32
31
A2 N2
(b) (i) X = A−1B A1 N1
(ii) X = ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
325
A3 N3
[6]
Matrices (GDC) IB Questionbank Maths SL 22
A10. (a) (i) a = 4 A1 N1
(ii) b = 7 A1 N1
(b) EITHER
A⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
12107
zyx
A1 N1
OR
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−−
12107
122113021
zyx
A1 N1
(c) ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛−
12107
1Azyx
(accept algebraic method) (M1)
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛−=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
453
zyx
(accept x = −3, y = 5, z = 4) A2 N3
[6]
Matrices (GDC) IB Questionbank Maths SL 23
A11. (a) q = 0 A1 N1
(b) Attempting to substitute (3, 18) (M1)
m33 + n32 + p3 = 18 A1 27m + 9n + 3p = 18 AG N0
(c) m + n + p = 0 A1 N1
− m + n − p = −10 A1 N1
(d) (i) Evidence of attempting to set up a matrix equation (M1)
Correct matrix equation representing the given equations A2 N3
eg ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−− 10018
1111113927
pnm
(ii) ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛−352
A1A1A1 N3
(e) Factorizing (M1)
eg f (x) = x(2x2 − 5x + 3), f (x) = (x2 − x)(rx − s)
r = 2 s = 3 (accept f (x) = x(x − 1)(2x − 3)) A1A1 N3 [14]
Matrices (GDC) IB Questionbank Maths SL 24
A12. (a) ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
−−
8.03.01.0
2.02.04.0
2.17.01.0
A2 3
(b) For recognizing that the equations may be written as A ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
321
zyx
(M1)
for attempting to calculate ⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛=
⎟⎟⎟
⎠
⎞
⎜⎜⎜
⎝
⎛−
6.16.02.1
321
1Azyx
M1
x = 1.2, y = 0.6, z = 1.6 (Accept row or column vectors) A2 3 [6]