А. b=ac/(a+c)
Б. b=ac/(c-a)
В. b=(a-c)/ac
Г. b=ac/(a-c)
\[\frac{1}{c} = \frac{1}{a} + \frac{1}{b}\]
\[\frac{1}{b} = \frac{1}{c} - \frac{1}{a}\]
\[\frac{1}{b} = \frac{a - c}{\text{ac}}\]
\[b = \frac{\text{ac}}{a - c}.\]
\[Ответ:\ \ г)\ .\]