Question 7:
--- 7(a)(i) ---
7(a)(i) | Expands M to get a linear
expression in k, using any row
or column. | 1.1a | M1 | M =(12−3k−3)−7(6−k−1)−3(9−6)
=4k−35
Cofactors are
9−3𝑘𝑘 𝑘𝑘−5 3
� −23 5 4 �
M-1 7𝑘𝑘+25 −𝑘𝑘−10 −15
=
1 9−3𝑘𝑘 −23 7𝑘𝑘+25
4𝑘𝑘 −35� 𝑘𝑘−5 5 −𝑘𝑘−10�
3 4 −15
Obtains matrix of
minors/cofactors with at least
four correct elements
PI transposed form.
Condone overall sign error on
each element. | 1.1b | B1
Obtains matrix of
minors/cofactors with at least
seven correct elements
PI transposed form.
Condone overall sign error on
each element. | 1.1b | B1
Obtains correct matrix of
minors/cofactors
PI transposed form.
Condone overall sign error on
each element. | 1.1b | B1
Obtains fully correct, simplified
answer | 1.1b | A1
Total | 5
Q | Marking instructions | AO | Marks | Typical solution
--- 7(a)(ii) ---
7(a)(ii) | Obtains correct answer for their
linear expression for M | 1.1b | B1F | 35
𝑘𝑘 ≠
4
Total | 1
Q | Marking instructions | AO | Marks | Typical solution
--- 7(b) ---
7(b) | Obtains their correct M-1,need
not be simplified. | 3.1a | B1F | x −6 −23 60 6
  −1  
y = 0 5 −15 3
    
15
 z    3 4 −15   1 
−45
−1 
= 0
 
15
  15  
3 
 
= 0
 
 −1
 
x = 3 , y = 0 , z = –1
6
 
M-1 3
Forms their product  
 1
 | 1.1a | M1
Obtains
x = 3 , y = 0 , z = –1 ACF
CSO | 1.1b | A1
Total | 3
Question total | 9
Q | Marking instructions | AO | Marks | Typical solution