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A First Course in Linear Algebra, 2017a

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3.1. Basic Techniques and Properties 127<br />

Exercise 3.1.7 Compute the determ<strong>in</strong>ant by cofactor expansion. Pick the easiest row or column to use.<br />

1 0 0 1<br />

2 1 1 0<br />

0 0 0 2<br />

∣ 2 1 3 1 ∣<br />

Exercise 3.1.8 F<strong>in</strong>d the determ<strong>in</strong>ant of the follow<strong>in</strong>g matrices.<br />

[ ] 1 −34<br />

(a) A =<br />

0 2<br />

⎡<br />

4 3<br />

⎤<br />

14<br />

(b) A = ⎣ 0 −2 0 ⎦<br />

0 0 5<br />

⎡<br />

⎤<br />

2 3 15 0<br />

(c) A = ⎢ 0 4 1 7<br />

⎥<br />

⎣ 0 0 −3 5 ⎦<br />

0 0 0 1<br />

Exercise 3.1.9 An operation is done to get from the first matrix to the second. Identify what was done and<br />

tell how it will affect the value of the determ<strong>in</strong>ant.<br />

[ ] [ ]<br />

a b<br />

a c<br />

→···→<br />

c d<br />

b d<br />

Exercise 3.1.10 An operation is done to get from the first matrix to the second. Identify what was done<br />

and tell how it will affect the value of the determ<strong>in</strong>ant.<br />

[ ] [ ]<br />

a b<br />

c d<br />

→···→<br />

c d<br />

a b<br />

Exercise 3.1.11 An operation is done to get from the first matrix to the second. Identify what was done<br />

and tell how it will affect the value of the determ<strong>in</strong>ant.<br />

[ ] [<br />

]<br />

a b<br />

a b<br />

→···→<br />

c d<br />

a + c b+ d<br />

Exercise 3.1.12 An operation is done to get from the first matrix to the second. Identify what was done<br />

and tell how it will affect the value of the determ<strong>in</strong>ant.<br />

[ ] [ ]<br />

a b<br />

a b<br />

→···→<br />

c d<br />

2c 2d

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