Đặt \(g\left(x\right)=f\left(x\right)-f\left(2x\right)\Rightarrow g'\left(x\right)=f'\left(x\right)-2.f'\left(2x\right)\)
\(g'\left(1\right)=5\Rightarrow f'\left(1\right)-2f'\left(2\right)=5\) (1)
\(g'\left(2\right)=7\Rightarrow f'\left(2\right)-2.f'\left(4\right)=7\) (2)
(1)+2.(2) \(\Rightarrow f'\left(1\right)-4f'\left(4\right)=19\)