Расчет: ldSf0e - 1

1

/ d

-

1

/ f

=
-

1

/ F

1

/ d

-

1

/ f

= -

1

/ F

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

1

/ d

= -

1

/ F

+

1

/ f

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

d =

1

/ (-

1

/ F

+

1

/ f

)

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