Followed the hint, F ′ ( x ) = f ′ ( f ( x ) ) f ′ ( x ) {\displaystyle F'(x)=f'(f(x))f'(x)} , F ′ ( 2 ) = f ′ ( f ( 2 ) ) f ′ ( 2 ) = f ′ ( 3 ) 4 = 1 / 2 ∗ 4 = 2 {\displaystyle F'(2)=f'(f(2))f'(2)=f'(3)4=1/2*4=2}
answer: 2 {\displaystyle \color {blue}2}
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