Page 95 - DMTH201_Basic Mathematics-1

Basic Mathematics – I

Notes
5 2
4. Let A
3 7
5 2
| | 35 6 41
A
3 7
Cofactor of 5 = + (7) = 7
Cofactor of 2 = (3) = 3 I column
Cofactor of 3 = ( 2) = 2

Cofactor of 7 = + (5) = 5 II column

7 2
Adj A
3 5

7 2 7 2
Adj A 3 5 41 41
A 1
A
| | 41 3 5
41 41

1 2 1
5. Let A 1 2 1
1 1 1

1 2 1
| | 1 2 1
A
1 1 1

1( 2 1) 2(1 1) 1( 1 2)
3 0 3 0

Since | | 0,A the inverse does not exist.

1 2 0
6. 3 1 5
4 7 1

1 2 0
A
| | 3 1 5
4 7 1
1( 1 35) 2( 3 20) 0(21 4)

36 46 10 0
Cofactor of 1 = + ( 1 35) = 36
Cofactor of 2 = ( 3 20) = 23 I column

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