www . seprodstore . com 85 7 1 . Let 2 1 6 4 5 1 1 2 4 � � � � � �� � � � � A , 3 0 4 � � � � � � �� � � � � B and x y z � � � � � �� � � � � X . ( a ) Write down �1 A . [ 2 ] ( b ) Solve X in the equation � AX B . [ 3 ] 2 . Let 2 0 5 1 2 8 6 1 3 � � � � � � � � � � � � � � � A . ( a ) Write down �1 A . [ 2 ] ( b ) Hence , solve the system 2 5 740 2 8 592 6 3 444 x z x y z x y z � � � ���� � � � � � � � . [ 4 ] 3 . Let 3 2 1 2 1 1 1 0 a � � � � � �� � � � � A , where a� . It is given that 1 1 1 0 1 1 1 0 1 2 � � � � � � � � �� � � � � � A . ( a ) Find a . [ 2 ] It is also given that 0 6 9 � � � � � �� � � � � B and x y z � � � � � �� � � � � X . ( b ) Solve X in the equation � AX B . [ 3 ] Exercise 27