4. Use the above arrow technique to compute the determinants of the following matrices. -2 7 6 a) A = 5 1 3 8 -2 4 C b) A = 2 L4 c −4 1 1 3 c² 2

Algebra and Trigonometry (6th Edition)
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ChapterP: Prerequisites: Fundamental Concepts Of Algebra
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Problem 1MCCP: In Exercises 1-25, simplify the given expression or perform the indicated operation (and simplify,...
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Determinants of 2 × 2 and 3 × 3 matrices can be evaluated very efficiently using the pattern
suggested below
all
a21
912
822
-
a) A =
In the 2 × 2 case, the determinant can be computed by forming the product of the entries on the
rightward arrow and subtracting the product of the entries on the leftward arrow.
In the 3 x 3 case we first recopy the first and second columns as shown in the figure, after
which we can compute the determinant by summing the products of the entries on the rightward
arrows and subtracting the products on the leftward arrows.
For example
-4
7
3 1
4 -2
258
3
6
9
=
all a12 013 911
922 923 821
a21
631
932
1
= -4
931
= (3)(-2) – (1)(4) = −10
-
C
b) A = 2
L4
b
Warning: This trick does not work for matrices of size 4 x 4 or higher.
= [45+84 +96] - [105-48-72] = 240
912
922
632
5
4. Use the above arrow technique to compute the determinants of the following matrices.
[-2 7 6
5
1 -2
3
8
4
-4
1
C-1
3231
Transcribed Image Text:Determinants of 2 × 2 and 3 × 3 matrices can be evaluated very efficiently using the pattern suggested below all a21 912 822 - a) A = In the 2 × 2 case, the determinant can be computed by forming the product of the entries on the rightward arrow and subtracting the product of the entries on the leftward arrow. In the 3 x 3 case we first recopy the first and second columns as shown in the figure, after which we can compute the determinant by summing the products of the entries on the rightward arrows and subtracting the products on the leftward arrows. For example -4 7 3 1 4 -2 258 3 6 9 = all a12 013 911 922 923 821 a21 631 932 1 = -4 931 = (3)(-2) – (1)(4) = −10 - C b) A = 2 L4 b Warning: This trick does not work for matrices of size 4 x 4 or higher. = [45+84 +96] - [105-48-72] = 240 912 922 632 5 4. Use the above arrow technique to compute the determinants of the following matrices. [-2 7 6 5 1 -2 3 8 4 -4 1 C-1 3231
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