Question

Как выразить f ????????????????????????????

Answer 1

$\frac{1}{F} - \frac{1}{d} = \frac{1}{f}$

$\frac{d-F}{Fd} = \frac{1}{f}$

$f= \frac{Fd}{d-F}$

Answer 2

1/F-1/d=1/f
d-f/fd=1/f
f=fd/d-f