Question 774893
{{{1/r}}} = {{{1/A}}}+{{{1/B}}}+{{{1/C}}} Solve for A
subtract 1/B and 1/C from both sides
{{{1/r}}}-{{{1/B}}}-{{{1/C}}} = {{{1/A}}}
Multiply both sides by A
A[{{{1/r}}}-{{{1/B}}}-{{{1/C}}}] = 1
divide both sides by [{{{1/r}}}-{{{1/B}}}-{{{1/C}}}]
A = 1/[{{{1/r}}}-{{{1/B}}}-{{{1/C}}}]