[CHAPTER 5: MATRIX]
EXAMPLE 7
Given B 4 6 . Find the determinant of matrix B.
3 8
SOLUTION
|B| = (4 × 8) − (6 × 3) = 32 − 18
|B| = 14
ii. FOR A 3 3MATRIX
For a 3 3 matrix (3 rows and 3 columns)
Formula
a b c The determinant is;
A d
e f A aei fh bdi fg cdh eg
g h i
EXAMPLE 8
6 1 1
C 4 2 5
2 8 7
Given;
Find the determinant of matrix C.
SOLUTION:
C 6 14 40 128 10 132 4
C 306
95
[CHAPTER 5: MATRIX]
LET’S PRACTICE 4
1. Find the determinant of matrix A.
A 2 5
1 3
2. Find the determinant of matrix B. Ans: 11
Ans: 10
B 3 2
1 4 Ans: 44
Ans: 4
3. Find the determinant of matrix M.
Ans: 266
3 0 1
96
M 2 5 4
3 1 3
4. Find the determinant of matrix N.
1 1 1
N 2 5
7
2 1 1
5. Find the determinant of matrix Z.
7 5 4
2 6
Z 4
2 3 4
[CHAPTER 5: MATRIX]
5.4 INVERSE MATRIX USING MINOR, COFACTOR AND ADJOIN
Ignore the values on the current row and column
Calculate the determinant of the remaining values
EXAMPLE 9
3 0 2
Given A 2 0 2
0 1 1 . Find the inverse matrix of A
SOLUTION:
STEP 1: DETERMINANT
A 30 2 0 22 0 6 4
A 10
STEP 2: MINOR
M indicates the minor of matrices A
m11 0 2 0 21 2 m12 2 2 21 20 2 m13 2 0 21 0 2
1 0 0 1
1 1
m21 0 2 0 2 2 m22 3 2 31 20 3 m23 3 0 31 0 3
1 1 0 1 0 1
m31 0 2 0 0 0 m32 3 2 3 2 22 10 m33 3 0 30 0 0
0 2 2 2 2 0
2 2 2
M 2 3 3
0 10 0
97
[CHAPTER 5: MATRIX]
STEP 3: COFACTOR
2 2 2 2 2 2
Cofactor 2 3 3 2 3 3
0 10 0 0 10 0
STEP 4: ADJOIN
“Transpose” all elements in previous matrix.
The elements of row will be elements of columns.
2 2 0
AdjA 2 3 10
2 3 0
STEP 5: INVERSE MATRIX
Formula;
A1 1 AdjA
A
1 1 0⎤
12 2 0 ⎡5 5 1⎥⎥
= 10 −2 3 10 = ⎢⎢− 1 5 0⎦⎥
2 −3 3
0 ⎢ 1 5 10
⎣
− 3 10
LET’S PRACTICE 5
1. Find the inverse matrix
1 0 3
C 2 2
1
0 1 3
Using minor, cofactor and adjoin.
5 3 6
Ans: 6 3 7
2 1 2
98
[CHAPTER 5: MATRIX]
2. Find the inverse matrix
2 1 0
3 1
M 1
3 0 1
Using minor, cofactor and adjoin.
3 1 1
Ans: 1942
4 4
1 1
2 2
3 7
4 4 4
3. Find the inverse matrix
3 1 6
B 2 0 4
1 2 3
Using minor, cofactor and adjoin.
4 92 2
32
Ans: 1 52
0
2 1
4. Find the inverse matrix
3 7 5
F 4 1 12
2 9 1
Using minor, cofactor and adjoin.
107 38 79
Ans: 327 327 327
28 13 16
327 327 327
38 41 25
327 327 327
99
[CHAPTER 5: MATRIX]
5.5 SIMULTANEOUS LINEAR EQUATION USING MATRIX
REMEMBER:-
i. The system must have the same number of equations as variables, that is, the
coefficient matrices of the system must be square.
ii. The determinant of the coefficient matrices must be non-zero. The reason, of
course, is that the inverse of a matrix exist precisely when its determinant is
non-zero.
5.5.1 SIMULTANEOUS EQUATION USING INVERSE MATRIX
METHOD
EXAMPLE 10
Given;
x 3y z 1
2x 5y 3
3x y 2z 2
Solve the simultaneous equation by using inverse matrix method.
SOLUTION:
STEP 1: Rewrite the system using matrix multiplication
1 3 1 x 1
y
2 5 0 3
3 1 2 z 2
STEP 2: Writing the coefficient matrix as A
x 1 1 3 1
A
y 3 Where A 2 5 0
z 2 3 1 2
100
[CHAPTER 5: MATRIX]
STEP 3: Formula
A1 1 AdjA
A
x 1
y
A 1 3
z 2
STEP 4: Determinant of A
A 15 2 0 1 32 2 0 312 1 5 3
A 9
STEP 5: Minor of A
m11 5 2 01 10 m12 2 2 03 4 m13 21 53 13
m21 3 2 11 7 m22 1 2 13 1 m23 11 33 10
m31 30 15 5 m32 10 12 2 m33 15 32 11
10 4 13
1 10
Minor 7
5 2 11
STEP 6: Cofactor of A
10 4 13 10 4 13
10
Cofactor 7 1 7 1 10
5 2 11 5 2 11
101
[CHAPTER 5: MATRIX]
STEP 7: Adjoin of A
10 7 5
AdjA 4 1 2
13 10 11
STEP 8: Inverse matrix of A
A1 1 AdjA
A
1 10 7 5
9 1
A1 4 10 2
13 11
STEP 9: Solve the equation
x 1 10 7 5 1
y 9 1
4 10 2 3
z 13 11 2
x 1 10 21 10
y 9
434
z 13 30 22
x 1 21
y 9 3
39
z
STEP 10: Find the x, y and z
x 7133
y
z 13
3
102
[CHAPTER 5: MATRIX]
LET’S PRACTICE 6
Solve the simultaneous equation below by using inverse matrix method.
x y z 3
1. 2x 3y 4z 23
3x y 2z 15
Ans: 2,1,4
x 2y z 7
2. 2x 3y 4z 3
xyz 0
Ans: 1,3,2
4x 2 y 2z 10
3. 2x 8 y 4z 32
30x 12 y 4z 24
Ans: 2,6,3
3x 2 y z 24
4. 2x 2 y 2z 12
x 5 y 2z 31
Ans: 3,4,7
5x 2y 4x 0
5. 2x 3y 5z 8
3x 4 y 3z 11
Ans: 2,1,3
103
[CHAPTER 5: MATRIX]
5.5.2 SIMULTANEOUS EQUATION USING CRAMER’s RULE
EXAMPLE 11
x 2 y 3z 5
Given 3x y 3z 4
3x 4 y 7z 7
Solve the simultaneous equation by using Cramer’s Rule.
SOLUTION:
STEP 1: Rewrite the system using matrix multiplication
1 2 3 x 5
3 y
3 1 4
3 4 7 z 7
STEP 2: Find the determinant
A 117 34 237 3 3 334 1 3
A 19 24 45
A 40
STEP 3: Construct another 3 matrices
5 2 3 1 5 3 1 2 5
1 3 4 3
Ax 4 Ay 3 Az 3 1 4
7 4 7 3 7 7 3 4 7
STEP 4: Find the determinant of each matrices
5 2 3
1 3 517 34 247 3 7 344 1 7 95 14 69 40
Ax 4
7 4 7
1 5 3
4 3 147 3 7 537 3 3 33 7 4 3 7 60 27 40
Ay 3
3 7 7
104
[CHAPTER 5: MATRIX]
1 2 5
Az 3 1 4 11 7 44 23 7 4 3 534 1 3 23 18 75 80
3 4 7
STEP 5: Solve the equation
x Ax 40 1
A 40
y AY 40 1
A 40
z Az 80 2
A 40
LET’S PRACTICE 7
Solve the simultaneous equation below by using Cramer’s Rule
2x 2 y 4z 22
1. 3x 5 y 2z 35
6x 3y 3z 21
4x y 2z 1 Ans: 2,9,2
2. 2x y 6z 3
Ans: 1,1,1
4x 6 y 3z 7
Ans: 2,3,1
5x 9 y 3z 40
3. 9x 4 y 2z 4 105
5x 7 y 4z 15
[CHAPTER 5: MATRIX]
4x 2 y 2z 4
4. 7x y 2z 22
2x 6 y z 26
4x 7 y 3z 37 Ans: 2,4,2
5. 2x 3y 6z 61 Ans: 5,5,6
2x 2 y 4z 44
106
[CHAPTER 6: VECTOR AND SCALAR]
VECTOR AND SCALAR
OBJECTIVES:
At the end of this topic, students should be able to:
i. define vector
ii. understand the operation of vector
iii. apply scalar (dot) product of two vectors
iv. apply vector (cross) product of two vectors
v. understand area of parallelogram
6.1 INTRODUCTION OF VECTOR
Physical quantities can be classified under two main headings – vectors and scalars.
VECTOR
Vector is a physical quantity which is specified by magnitude or length and a
direction in space.
For example, displacement and velocity are both specified by a magnitude and a
direction and are therefore examples of a vector quantities.
SCALAR
Scalar is a physical quantity which is specified by just its magnitude.
For example, distance and speed are both fully specified by a magnitude and are
therefore examples of scalar quantities.
VECTOR NOTATION
Vectors are written as Y, y, ỹ or Y .
The magnitude of a vector Y is written as Y .
107
[CHAPTER 6: VECTOR AND SCALAR]
VECTOR REPRESENTATION
A vector is represented by a straight line with an arrowhead.
Figure 1
In the Figure 1, the line OA represents a vector OA .
You can write:
OA 24
which means that to go from O to A, move 4 units in the positive x
direction and 2 units in the positive y direction. This is called the column
vector or matrix form.
In Cartesian form, the vector OA can be represented as
OA 4i 2 j
Then,
OA 4 4i 2 j
2
VECTOR MAGNITUDE
The magnitude or modulus of the vector OA is represented by the length OA and its
donated by OA .
108
[CHAPTER 6: VECTOR AND SCALAR]
EXAMPLE 1
By referring Figure 2;
Figure 2 Angle;
The magnitude of a vector;
tan 1 y
OA x 2 y 2 x
OA 42 22
OA 20units tan 1 2
4
26.570
LET’S PRACTICE 1
1. Find the magnitude of each of these vectors.
a. 4i 3 j b. 2i 2 j k
c. 79 d. 57
3
Ans: 5 , 3 , 11.40 & 9.11
109
[CHAPTER 6: VECTOR AND SCALAR]
EQUALITY OF VECTORS
Two vectors are said to be equal if they have the
same magnitude and direction.
NEGATIVE VECTOR
A vector having the same magnitude but opposite
direction.
UNIT VECTOR
A unit vector is a vector of length 1.
unit vector, uˆ u
u
EXAMPLE 2
1. Find the unit vector in the direction of v = 5i – 2j +4k.
SOLUTION:
magnitude of v, v 52 22 42 45
if vˆ is a unit vector in the direction of v:
vˆ 5i 2 j 4k 4k
45 45
vˆ 5 i 2 j
45 45
110
[CHAPTER 6: VECTOR AND SCALAR]
LET’S PRACTICE 2
1. Find a unit vector in the direction of the vector 8i 6 j .
Ans: 4i 3 j
5
2. Find a unit vector in the direction of v 3i 2 j 5k .
3. Find a unit vector in the direction of the vector 7 Ans: 3i 2 j 5k
9 38
Ans: 7i 9 j
130
4. Find a unit vector in the direction of the vector 123
4
Ans: 3i 12 j 4k
13
111
[CHAPTER 6: VECTOR AND SCALAR]
POSITION VECTORS
By referring to the Figure 3, the position vector of a point P with respect to a
fixed origin O is the vector OP.
This is not a free vector, since O is fixed point.
It can be write as; OP P
Then,
PQ PO OQ
PQ P Q
PQ Q P
Figure 3
EXAMPLE 3
7 5
1. Given that a 3 and b 2 , find ab and ab . Hence, find unit vector
2 3
in the direction of a b .
SOLUTION:
→ + → = 7 −5 2
3 + 2 =5
−2 3 1
→ + → = 2 + 5 + 1 = √30
a a
b a b
Unit vector, b
a 2i 5 j k 2 i 5 j 1k
b 30 30 30
30
112
[CHAPTER 6: VECTOR AND SCALAR]
2. Given that OX 6i 3 j k and OY 2i 4 j 5k . Find the unit vector in the
direction of XY .
SOLUTION:
XY OY OX
2 6 4
3
XY 4 7
5 1 6
XY 42 7 2 62 101
Unit vector, XY XY
XY
XY 4i 7 j 6k
101
XY 4 i 7 j 6k
101 101 101
LET’S PRACTICE 3
1
1. If given B 3 , find the unit vector of B .
2
Ans: 1 i 3 j 2 k
14 14 14
113
[CHAPTER 6: VECTOR AND SCALAR]
2. If given vector A 2i 3 j 6k and B i j 2k . Find
a. 2A B
b. 2A B
c. Unit vector of 2A B
Ans: 5i 5 j 14k , 246 & 5 i 5 j 14 k
246 246 246
3. Find the unit vector of BA if given OA i 5 j 12k and OB 3i 5 j k .
Ans: 2 i 11 k
125 125
6.2 THE OPERATION OF VECTOR
6.2.1 VECTOR ADDITION
Figure 4
By referring the Figure 4 above;
OR OP PR OR OQ QR
i) OR A B C ii) OR A B C
From i) and ii)
OR A B C A B C
114
[CHAPTER 6: VECTOR AND SCALAR]
6.2.2 ADDITION AND SUBTRACTION OF VECTOR USING PARALLELOGRAM
METHOD
PARALLELOGRAM is a quadrilateral with both pairs of opposite sites parallel.
Quadrilateral are four side polygons.
Congruent refer to a shape (in mathematics) that has the same shape and size as
another.
Properties of Parallelogram
Figure 5
PROPERTIES
i. If a quadrilateral is a parallelogram, then its opposite sides are congruent.
PQ RS and SP QR
ii. If a quadrilateral is a parallelogram, then its opposite angles are congruent.
P R and Q S
iii. If a quadrilateral is a parallelogram, then its consecutive angles are
supplementary.
P Q 180 0 R S 180 0
Q R 180 0 S P 180 0
iv. If a quadrilateral is a parallelogram, then its diagonals bisect each other
QM SM and PM RM
115
[CHAPTER 6: VECTOR AND SCALAR]
EXAMPLE 4
Figure 6
ABCD is a parallelogram, find the sum of vectors below in unit of vector guide.
i. DA AC
ii. AD AB
iii. AB CB
Solution:
i. DA AC DC
ii. AD AB AC
iii. AB CB DB
6.2.3 ADDITION AND SUBTRACTION OF VECTOR USING TRIANGLE RULE
Another way to define addition of two vectors is by a head-to-tail construction
that creates two sides of a triangle.
The third side of the triangle determines the sum of the two vectors.
Figure 7
The vector u v is defined to be the vector OP
116
[CHAPTER 6: VECTOR AND SCALAR]
EXAMPLE 5
Figure 8
ABCD is a triangle where BC CD DE . Given AB 6a 4b and BC a b . Express
the followings in term of a and b.
i. ED
ii. AC
iii. DA
SOLUTION:
i. ED CB BC a b b a
AC AB BC
ii. AC 6a 4b a b
AC 7a 3b
DA DB BA
iii. DA 2a b 6a 4b
DA 2a 2b 6a 4b
DA 8a 2b
117
[CHAPTER 6: VECTOR AND SCALAR]
LET’S PRACTICE 4
1. Given that FGHJ is a parallelogram, find MH and FH. Given FM 5
Figure 9
Ans: 5,10
2.
Figure 10
ABCD is a parallelogram, find the sum of vectors below in unit of vector guide.
a. AB BD
b. CO OD Ans: AD
c. CA BC Ans: CD
d. OB DO Ans: BA
Ans: DB
118
[CHAPTER 6: VECTOR AND SCALAR]
LET’S PRACTICE 5
O, A, B,C and D are five points where OA a , OB b , OC a 2b and OD 2a b .
Express AB, BC,CD, AC and BD in terms of and .
Ans:
AB b a
BC a b
CD a 3b
AC 2b
BD 2a 2b
LET’S PRACTICE 6
is a parallelogram with VW a and WX b . Express the vectors below in terms
of and .
i. VX
Ans: a b
ii. XV
Ans: b a
iii. WY
Ans: b a
iv. YW
Ans: a b
119
[CHAPTER 6: VECTOR AND SCALAR]
6.3 APPLY SCALAR (DOT) PRODUCT OF TWO VECTORS
Definition of scalar product
In Figure, ⃗ = and ⃗ = . Figure
The angle between and is defined as the
angle between ⃗ and ⃗ .
The scalar product of a vector and is
represented by ∙ , and
∙ = | || | cos , with as the angle
between and .
as the angle between and , then ∙ = | || | cos .
Therefore, cos = ∙
| || |
+
cos =
( ) +( ) ( ) +( )
Properties of scalar product
i.
AB B A
ii. For non zero vector A and B ;
0; If and only if is perpendicular to
B A A B
A BC AB AC
iii.
A kB kA B k A B
iv.
v. If vectors and are given in term of their component with respect to the
A B
standard vectors i, j and k as
A a1i a2 j a3k and B b1i b2 j b3k
Then;
A B a1b1 a2b2 a3b3
120
[CHAPTER 6: VECTOR AND SCALAR]
EXAMPLE 6
1. If = 2 + and = − 3 . Find
a. ∙
b. ∙ ( − )
c. (10 + ) ∙
d. (3 ∙ ) ∙
SOLUTION:
a. ∙ = (2 × 1) + [1 × (−3)] = 2 − 3
∙ = −
b. ∙ ( − ) = (2 + ) ∙ [( − 3 ) − (2 + )]
∙ ( − ) = (2 + ) ∙ (− − 4 )
∙ ( − ) = [2 × (−1)] + [1 × (−4)]
∙ ( − ) = −
c. (10 + ) ∙ = [10(2 + ) + ( − 3 )] ∙ ( − 3 )
(10 + ) ∙ = [(20 + 10 ) + ( − 3 )] ∙ ( − 3 )
(10 + ) ∙ = (21 + 7 ) ∙ ( − 3 )
(10 + ) ∙ = (21 × 1) + [7 × (−3)]
( + ) ∙ =
d. (3 ∙ ) ∙ = [3(2 + )] ∙ ( − 3 ) ∙ (2 + )
(3 ∙ ) ∙ = [(6 + 3 ) ∙ ( − 3 )] ∙ (2 + )
(3 ∙ ) ∙ = [(6 × 1) + 3(−3)] ∙ (2 + )
(3 ∙ ) ∙ = (−3) ∙ (2 + )
( ∙ ) ∙ = − −
121
[CHAPTER 6: VECTOR AND SCALAR]
2. A, B and C are three points with ⃗ = 2 + and ⃗ = + 3 . Find angle .
SOLUTION:
⃗ = − ⃗ = −2 −
⃗ ∙ ⃗
cos = ⃗ ⃗
(−2 − ) ∙ ( + 3 )
cos =
(−2) +(−1) (1) +(3)
−2 − 3
cos =
√5√10
−2 − 3
∠ = cos
√5√10
∠ = °
3. The position vectors of points A, B and C, relative to the origin O, are
−4 , 0 0 respectively, with a > 0. Calculate:
−2 2
a. The scalar product of ⃗ . ⃗
b. Angle
SOLUTION:
a. The scalar product of ⃗ . ⃗
⃗ = ⃗ − ⃗
⃗ = 0 − −4 = 4
−2 −3
⃗ = ⃗ − ⃗
⃗ = 0 − −4 = 4
2
⃗ . ⃗ = (4 )(4 ) + (−3 )( )
⃗ . ⃗ = 16a
122
[CHAPTER 6: VECTOR AND SCALAR]
b. Angle
⃗ . ⃗
cos = ⃗ ⃗
16a
cos =
(4 ) +(−3 ) (4 ) +( )
16a
cos =
√25 √17
16a
cos = (5 )(4.123 )
∠ = cos 0.6306 = . °
LET’S PRACTICE 7
1. If P 2i 4 j 6k and U 2i 4 j 3k . Find
a.
P U
b. P U P
2. Given A4,4,8, B5,1,8 and C 2,4,3. Find: Ans: 38 , 76i 152 j 228k
i. Ans: 80
A B Ans: 32
ii.
AC
iii.
BC
Ans: 10
123
[CHAPTER 6: VECTOR AND SCALAR]
6.4 APPLY VECTOR (CROSS) PRODUCT OF TWO VECTORS
Properties of vector product
If A, B and C are vectors and d is a scalar, then
i. A B B A
ii. dA B d A B A dB
iii. A B C A B A C
iv. A B C A C B C
v A BC A B C
vi. A B C A CB A BC
EXAMPLE 7
1. Find the vector product for vector A 2i 2 j 2k and B 2i 2 j 3k . Find
SOLUTION:
i j k
A B 2 2 2
2 2 3
23 2 2i 23 22j 2 2 22k
2i 10 j 8k
2. Find the unit vector of u v . Given u 2i 2 j 3k and v i 3 j k .
SOLUTION:
i j k
u v 2 2 3 11i 5 j 4k
1 3 1
124
[CHAPTER 6: VECTOR AND SCALAR]
u v 112 52 42 162
Vector unit of u v is; 11 i 5 j 4k
162 162 162
LET PRACTICE 8
1. Given vector OA 2i j 3k , OB 3i 2 j 4k and OC i 3 j 2k . Determine
a. AB
b. OA OBOC Ans: i 3 j 7k
c. OAOB OC Ans: 39
Ans: 55i 11j 11k
2. If P 8i 5 j 4k and Q 2i 7 j 4k , find:
Ans: 48i 24 j 66k
a. Q P Ans: 48i 24 j 66k
Ans: 8i 13 j 10k
Ans: 8i 13 j 10k
b. P Q
125
3. If a 3i 2 j 5k and b i 4 j 6k , find:
a. a b
b. b a
[CHAPTER 6: VECTOR AND SCALAR]
6.4.1 APPLICATION OF THE VECTOR (CROSS) PRODUCT
Area of parallelogram
AB AC sin
AB BC
Area of triangle ABC
1 AB BC
2
EXAMPLE 8
1. Find the area of the parallelogram with vertices A0,5, B2,0 , C8,1 and
D 6,4.
SOLUTION:
AB 2,5 2i 5 j 0k
BC 6,1 6i j 0k
Area of parallelogram Area AB BC
i jk
AB BC 2 5 0
6 1 0
AB BC 0i 0 j 28k
AB BC 02 02 282 28
2. Calculate the area of the parallelogram spanned by the vectors
3 and 4
P 3 Q 9
1 2
126
[CHAPTER 6: VECTOR AND SCALAR]
SOLUTION:
P 3,3,1 3i 3 j k
Q 4,9,2 4i 9 j 2k
Area of parallelogram Area P Q
i jk
PQ 3 3 1
492
P Q 6 9i 6 4 j 27 12k
P Q 15i 2 j 39k
P Q 152 22 392 41.83
LET PRACTICE 9
1. Find the area of parallelogram with vertices A0,0, B2,1 , 3,6 and D 1,5.
C
Ans: 9
2. Find the area of parallelogram with U i j 3k and V 6 j 5k .
Ans: 230
3. Find the area of triangle with vertices P1,1,0, Q 2,0,1 and R0,2,3.
Ans: 4.899
127
[CHAPTER 6: VECTOR AND SCALAR]
4. Find the area of parallelogram with vertices P1,5,3, Q0,0,0 and R3,5,1.
Ans: 24.5
5. Find the area of parallelogram with vertices x2,0,3, y1,4,5, and z7,2,9.
Ans: 64.9
128
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Pearson.
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Learning.
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Published