Algebra 1 Common Core Student Edition, Grade 8-9

You may need to add or subtract matrices in order to solve problems. You can only add

or subtract matrices that are the same size. You add or subtract matrices by adding or

subtracting the corresponding elements.

1 l i i n i c
Can you add t he
matrices?
Yes, you can add the
matrices because they
are the same size. Each
matrix has 2 rows and
2 columns.

Adding and Subtracting M atrices

What is each sum or difference?

'-5 2.7'

+

-3 -3.9 = '-5 + (-3) 2.7 + (-3.9)'

7 -3 .- 4 (^2) .7 + (- 4 ) -3 + 2
Add
corresponding
elements.
-8 -1.2
3 -1
Simplify.
o
2 11 "-1 8~ 2 — (—1) 11-8

• 4 3.2 - -6.5 4 =-4- (-6.5)3.2-4

1.5 -5 (^0) -3 1.5-0 -5-(-3)
3 3
2.5 -0.8
1.5 - 2
Subtract
corresponding
elements.
Simplify.
Go t It? 1. What is each sum or difference in parts (a) and (b)?
5-9
a. 3.2 + -1.7
-4.9 -11.1
'-4 o’ -5 -1

37. 0.5-3,

b.

c. Reaso n i n g Explain why you cannot add or subtract matrices that are not

the same size.

Think
Which factor is the
scal ar?
The scalar is the real-
number factor, 3.

You may also need to multiply a matrix by a real number in order to solve problems.

The real-number factor is called a scal ar. Multiplying a matrix by a scalar is called

scal ar m u l t i p l i cat i o n. To use scalar multiplication, multiply each element in the matrix

by the scalar.

Multiplying a Matrix by a Scalar

What is the product 3

4 -1 .5

1 -6

3

'4 -1.5' "3(4) 3( 1.5)”

.1 -6 .3(1) 3( 6).

12 -4.5'

3-18

M u ltip ly each e le m e n t by th e scalar, 3.

Simplify.

Po w er A Ig eb r a.co m Lesso n 12-1 Organizing Data Using M atrices^727