9 . Let f ( x) 30 9x 2x
2 3
� � � .
( a ) |
Find f�
( x)
.
|
( b ) |
Hence , solve the equation f�( x)
�
0.
|
( c ) |
( i ) |
Write down f��
( x)
.
|
[ 2 ]
[ 2 ]
( ii ) Hence , determine the x -coordinate of the local maximum of f .
( iii ) Write down the y -coordinate of the local maximum of f . [ 4 ]
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