15 . The function f is defined as restricted as { x : x � k} such that
f ( x) ( x 10 ) ( x 2 )
2 2
� � � . The domain of f is
1 f � exists .
( a ) Write down the coordinates of the local minimum of f which is closest to the origin .
[ 1 ]
( b ) Hence , write down the minimum value of k . [ 1 ] f can also be expressed as f ( x) (( 4 ) 36 )
2 2
� x � � .
( c ) Find the expression of
1 f � . [ 3 ]
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