Question 894214
Solve for r in:
{{{e/d=R+r/r}}}


Multiply both members by r.
{{{er/d=Rr+r^2}}}

{{{r^2+Rr-er/d=0}}}

{{{r^2+(R-e/d)r=0}}}

{{{r(r+(R-e/d))=0}}}


Either r=0 which probably not what you want and will not work in the original equation;
Or {{{highlight(r=e/d-R)}}}.



QUESTION:
Why do you show r used in the equation in the expression of {{{r/r}}}?
This is simply equal to 1.