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1202 ⏐⏐⏐ APPENDIXES<br />

x �<br />

Warning: This method of expansion is good only for third-order<br />

determinants! It cannot be applied to fourth- and higher-order systems.<br />

EXAMPLE C.5 Evaluate the following determinant:<br />

1<br />

�2<br />

0<br />

Solution:<br />

[(1)(1)(2) � (2)(0)(0) � (3)(�2)(4)]<br />

�[(0)(1)(3) � (4)(0)(1) � (2)(�2)(2)]<br />

� (2 � 0 � 24) � (0 � 0 � 8) � (�22) � (�8)<br />

��22 � 8 � �14<br />

EXAMPLE C.6 Solve for x, y, and z:<br />

1x � 0y � 2z ��1<br />

0x � 3y � 1z ��2<br />

1x � 2y � 3z � 0<br />

Solution:<br />

2<br />

1<br />

4<br />

3<br />

0<br />

2<br />

1<br />

�2<br />

0<br />

2<br />

1<br />

4<br />

3<br />

0<br />

2<br />

(�) (�) (�)<br />

1<br />

�2<br />

0<br />

2<br />

1<br />

4<br />

(�) (�) (�)<br />

[(�1)(3)(3) � (0)(1)(0) � (�2)(2)(2)] � [(0)(3)(�2) � (2)(1)(�1) � (3)(2)(0)]<br />

� ���������<br />

[(1)(3)(3) � (0)(1)(1) � (�2)(0)(2)] � [(1)(3)(�2) � (2)(1)(1) � (3)(0)(0)]<br />

�<br />

� � � 15 (�9 � 0 � 8) � (0 � 2 � 0)<br />

����<br />

(9 � 0 � 0) � (�6 � 2 � 0)<br />

�17 �2<br />

� -<br />

9 � 4 13<br />

y �<br />

�<br />

�1<br />

2<br />

0<br />

1<br />

0<br />

1<br />

1<br />

0<br />

1<br />

�1<br />

2<br />

0<br />

13<br />

0<br />

3<br />

2<br />

0<br />

3<br />

2<br />

�2<br />

1<br />

3<br />

�2<br />

1<br />

3<br />

�2<br />

1<br />

3<br />

�1<br />

2<br />

0<br />

1<br />

0<br />

1<br />

1<br />

0<br />

1<br />

�1<br />

2<br />

0<br />

0<br />

3<br />

2<br />

0<br />

3<br />

2<br />

[(1)(2)(3) � (�1)(1)(1) � (�2)(0)(0)] � [(1)(2)(�2) � (0)(1)(1) � (3)(0)(�1)]<br />

���������<br />

13<br />

�<br />

� � 9 (6 � 1 � 0) � (�4 � 0 � 0)<br />

����<br />

13<br />

5 � 4<br />

� -<br />

13 13

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