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082-Engineering-Mathematics-Anthony-Croft-Robert-Davison-Martin-Hargreaves-James-Flint-Edisi-5-2017

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260 Chapter 8 Matrix algebra

The resultobtained inExample 8.3 istruemore generally:

Matrix addition iscommutative, thatis

A+B=B+A

Itis alsoeasytoshow that

Matrix addition isassociative, that is

A+(B+C)=(A+B)+C

8.3.2 Scalarmultiplication

GivenanymatrixA,wecanmultiplyitbyanumber,thatisascalar,toformanewmatrix

of the same order asA. This multiplication is performed by multiplying every element

ofAby the number.

Example8.4 If

⎛ ⎞

1 3

A = ⎝−2 1⎠

0 1

find 2A, −3Aand 1 2 A.

⎛ ⎞ ⎛ ⎞

1 3 2 6

Solution 2A=2⎝−2 1⎠ = ⎝−4 2⎠

0 1 0 2

⎛ ⎞

1 3

⎛ ⎞

−3 −9

−3A = −3⎝−2 1⎠ = ⎝ 6 −3⎠

0 1 0 −3

and

1

⎛ ⎞

1

2 A = 1 1 3

2

⎝−2 1⎠ =

−1

2 ⎜

0 1 ⎝

0

3

2

1

2⎟

1

2

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