15 . A quadratic function is given by
2 f ( x) ax bx c � � � . It is given that the complex roots of f( x) � 0 are 1 � 1 i and 1 � 1 i . 2 4 2 4
( a ) Write down the values of
( i )
( ii )
� 1 1 1 1 � � i � �+
� � � i �
� � 2 4 � � 2 4 � ;
� 1 1 1 1 � � i �� �� � i �
� � 2 4 �� 2 4 � . [ 2 ]
( b ) Hence , find the expression of f( x ), giving the answer in terms of a .
The graph of f( x ) passes through
� 5 � �1 , � � 2 � .
[ 3 ]
( c ) Find the value of a . [ 2 ]
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