The table shows the top scores for girls in barrel racing at the 2004 National High School Rodeo finals. The data can be presented in a table or a spreadsheet as rows and columns of numbers.
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The table shows the top scores for girls in barrel racing at the 2004 National High School Rodeo finals. The data can be presented in a table or a spreadsheet as rows and columns of numbers.
You can also use a the 2004 National High School Rodeo finals. The data can be presented in a table or a spreadsheet as rows and columns of numbers. matrix to show table data. A matrix is a rectangular array of numbers enclosed in brackets.
Matrix A has two rows and three columns. A matrix with m rows and n columns has dimensionsm n, read “m by n,” and is called an mn matrix. Matrix A has dimensions 2 3. Each value in a matrix is called an element of the matrix.
We the 2004 National High School Rodeo finals. The data can be presented in a table or a spreadsheet as rows and columns of numbers. name an element by its location in a matrix, where the number of the Row comes first, and then the number of the Column. This can also be expressed by using the lower case matrix letter with row and column number as subscripts.
The score 16.206 is located in row 2 column 1, so the name of this element is a2,1 (or Row 2, Column 1), and it’s value is 16.206.
3.95 5.95 the 2004 National High School Rodeo finals. The data can be presented in a table or a spreadsheet as rows and columns of numbers.
3.75 5.60
3.50 5.25
P =
Example 1: Displaying Data in Matrix Form
The prices for different sandwiches are presented at right.
A. Display the data in matrix form.
B. What are the dimensions of P?
P has three rows and two columns, so it is a 3 2 matrix.
Example 2: Displaying Data in Matrix Form the 2004 National High School Rodeo finals. The data can be presented in a table or a spreadsheet as rows and columns of numbers.
The prices for different sandwiches are presented at right.
C. What is element P3,2? What does is represent?
The entry at P3,2, in row 3 column 2, is 5.25. It is the price of a 9 in. tuna sandwich.
D. What is the name of the element 5.95?
The element 5.95 is P1,2. It is Row 1 Column 2
Check It Out! the 2004 National High School Rodeo finals. The data can be presented in a table or a spreadsheet as rows and columns of numbers. Example 1
Use matrix M to answer the questions below.
a. What are the dimensions of M?
3 4
b. What is the value of m3,2?
11
c. The entry 0 appears for which two elements?
m1,4 and m2,3
Example 3: Point Matrices the 2004 National High School Rodeo finals. The data can be presented in a table or a spreadsheet as rows and columns of numbers.
Points in the coordinate plane can also be represented by a matrix. This is called aPoint Matrix.
Row 1 is always representing the xcoordinate, and Row 2 is always representing the ycoordinate. So any point matrix will only ever have 2 rows, since coordinates only have two values.
x
y
(x,y) =
Triangle ABC is graphed in the coordinate plane on the left. Write its vertices as a point matrix.
The xcoordinates become the elements in the first row of the matrix.
A = (1, 1)
B = (1, 3)
C = (1, 2)
The ycoordinates become the elements in the 2nd row of the matrix.
A B C
X
Y
1 1 1
1 3 2
Triangle A’B’C’ is graphed in the coordinate plane on the left. Write its vertices as a point matrix.
Put the xcoordinates as the elements in the first row of the matrix.
A’ = (1, 1)
B’ = (3, 1)
C’ = (2, 1)
Put the ycoordinates as the elements in the 2nd row of the matrix.
A’ B’ C’
X
Y
1 3 2
1 1 1
You can add or subtract two matrices only if they have the same dimensions.
If the dimensions are the same, then you can add the corresponding elements: Those that are in the same location in each matrix (those with the same name)
3 –2 same dimensions.
1 0
3 + 1–2 + 4
1 + (–2)0 + 3
4 2
–1 3
+
=
=
1 4
–2 3
Example 2A: Finding Matrix Sums and Differences
Add or subtract, if possible.
3 –2
1 0
4 7 2
5 1 –1
1 4
–2 3
2 –2 3
1 0 4
W = ,
X = ,
Y = ,
Z =
W + Y
Add each corresponding entry.
W + Y =
2 –2 3 same dimensions.
1 0 4
4 7 2
5 1 –1
2 9 –1
4 1 –5
–
=
Example 2B: Finding Matrix Sums and Differences
Add or subtract, if possible.
3 –2
1 0
4 7 2
5 1 –1
1 4
–2 3
2 –2 3
1 0 4
W = ,
X = ,
Y = ,
Z =
X – Z
Subtract each corresponding element.
X – Z =
Example 2C: Finding Matrix Sums and Differences same dimensions.
Add or subtract, if possible.
3 –2
1 0
4 7 2
5 1 –1
1 4
–2 3
2 –2 3
1 0 4
W = ,
X = ,
Y = ,
Z =
X + Y
X is a 2 3 matrix, and Y is a 2 2 matrix. Because X and Y do not have the same dimensions, they cannot be added.
4 0 –8 same dimensions.
6 2 18
4 –1 –5
3 2 8
0 1 –3
3 0 10
4 + 0 –1 + 1 –5 + (–3)
3 + 3 2 + 0 8 + 10
+
=
Check It Out! Example 2A
Add or subtract if possible.
4 –2
–3 10
2 6
3 2
0 –9
–5 14
4 –1 –5
3 2 8
0 1 –3
3 0 10
A = ,
C = ,
D =
B = ,
B + D
Add each corresponding entry.
B + D =
Check It Out! same dimensions. Example 2B
Add or subtract if possible.
4 –2
–3 10
2 6
3 2
0 –9
–5 14
4 –1 –5
3 2 8
0 1 –3
3 0 10
A = ,
C = ,
D =
B = ,
B – A
B is a 2 3 matrix, and A is a 3 2 matrix. Because B and A do not have the same dimensions, they cannot be subtracted.
0 1 –3 same dimensions.
3 0 10
4 –1 –5
3 2 8
–4 2 2
0 –2 2
–
=
Check It Out! Example 2C
Add or subtract if possible.
4 –2
–3 10
2 6
3 2
0 –9
–5 14
4 –1 –5
3 2 8
0 1 –3
3 0 10
A = ,
C = ,
D =
B = ,
D – B
Subtract corresponding entries.
D – B =
0 1 –3 same dimensions.
3 0 10
4 –1 –5
3 2 8
4 0 8
6 2 18
+
=
Commutative Property
We already found B+D, Now find D+B
4 –2
–3 10
2 6
3 2
0 –9
–5 14
4 –1 –5
3 2 8
0 1 –3
3 0 10
A = ,
C = ,
D =
B = ,
D+B =
Are the results the same?
Yes! So Matrix Addition is Commutative
4 1 –5 same dimensions.
3 2 8
0 1 3
3 0 10
4 2 2
0 2 2
–
=
Commutative Property
We already found DB, NOW find BD:
4 –2
–3 10
2 6
3 2
0 –9
–5 14
4 –1 –5
3 2 8
0 1 –3
3 0 10
A = ,
C = ,
D =
B = ,
BD
Subtract corresponding entries.
BD =
Are the results the same?
NO! So, Matrix Subtraction is NOT Commutative
Consider Three Matrices: A,B, and C. Assuming that they all have the same dimensions, Would changing the grouping affect the result of Matrix Addition?
Does A+(B+C) = (A+B)+C ????
YES! So, Matrix Addition is also Associative
Would changing the grouping affect the result of Matrix Subtraction?
Does A(BC) = (AB)C ????
NO! So, Matrix Subtraction is also NOT Associative
You can multiply a matrix by a number, called a same dimensions.scalar. To find the product of a scalar and a matrix, or the scalar product, multiply each element by the scalar.
30 17.5 same dimensions.
25 14
40 22.5
150 87.5
125 70
200 112.5
150 87.5
125 70
200 112.5
150 87.5
125 70
200 112.5
–
120 70
100 56
160 90
Check It Out! Example 4
Use a scalar product to find the prices if a 20% discount is applied to the ticket service prices.
You can multiply by 0.2 and subtract from the original numbers.
– 0.2
=
Example 4b: Simplifying Matrix Expressions same dimensions.
3 –2
1 0
2 –1
1 4
–2 3
0 4
4 7 2
5 1 –1
P =
R =
Q=
Evaluate 3P — Q, if possible.
P and Q do not have the same dimensions; they cannot be subtracted after the scalar products are found.
3 12 same dimensions.
–6 9
0 12
1 4
–2 3
0 4
3 –2
1 0
2 –1
3 –2
1 0
2 –1
3(1) 3(4)
3(–2) 3(3)
3(0) 3(4)
3 –2
1 0
2 –1
=
= 3
–
–
–
0 14
–7 9
–2 13
Example 4c: Simplifying Matrix Expressions
3 –2
1 0
2 –1
1 4
–2 3
0 4
4 7 2
5 1 –1
P =
R =
Q=
Evaluate 3R — P, if possible.
=
Check It Out! same dimensions. Example 4d
4 –2
–3 10
4 –1 –5
3 2 8
3 2
0 –9
D = [6 –3 8]
A =
B =
C =
Evaluate 3B + 2C, if possible.
B and C do not have the same dimensions; they cannot be added after the scalar products are found.
4 –2 same dimensions.
–3 10
3 2
0 –9
= 2
–3
8 –4
–6 20
9 6
0 27
–1 –10
–6 47
2(4) 2(–2)
2(–3) 2(10)
3(3) 3(2)
3(0) 3(–9)
=

=
=

Check It Out! Example 4e
4 –2
–3 10
4 –1 –5
3 2 8
3 2
0 –9
D = [6 –3 8]
A =
B =
C =
Evaluate 2A – 3C, if possible.
Check It Out! same dimensions. Example 4f
4 –2
–3 10
4 –1 –5
3 2 8
3 2
0 –9
D = [6 –3 8]
A =
B =
C =
Evaluate D + 0.5D, if possible.
= [6 –3 8] + 0.5[6 –3 8]
= [6 –3 8] + [0.5(6) 0.5(–3) 0.5(8)]
= [6 –3 8] + [3 –1.5 4]
= [9 –4.5 12]
Lesson Quiz same dimensions.
1. What are the dimensions of A?
2. What is entry D1,2?
Evaluate if possible.
3.10(2B + D)4.C + 2D 5. Graph D in the coordinate plane as ΔABC
3 2
–2
Not possible
C.
A.
B.