Page 509 - เตรียมสอบครูผู้ช่วยคอมพิวเตอร์_compressed

= ( ) 06 −−
= –6

− 9  3
5.3 A =  
 − 4 3 
det (A) = [ 9(− )× 3 ] [ 4(−− )× ] 3

= –27 + 12

= –15

 1 0 3 
 
5.4 A = − 2 5 −1
 
 2 4 −  3 

1 0 3 1 0
det (A) = − 2 5 − 1 − 2 5

2 4 − 3 2 4

3
1
(
3
= [ ×51 ×( − ) ]+ 0( ×( − ) × ) + 3 ×( − ) × ) − 2 ×5 × ) −
4
2
(
2
4( × (− ) 1 × ) 1 − [ 3(− )× (− ) 2 × ] 0
= –15 + 0 – 24 – 30 + 4 – 0
= –65
2 1 −  2
 
5.5 A = 3 −1 0
 
2 5 3 


2 1 − 2 2 1
det (A) = 3 − 1 0 3 − 1
2 5 3 2 5

= 2( × (− ) 1 × ) 3 + 1 ( × 0× ) 2 + [ 2(− )× 3× 5 ] [2×− (− ) 1 × (− ] ) 2

(5 0 2) (3 3 1)− × × − × ×

= –6 + 0 – 30 – 4 – 0 – 9

= –49