Question 1097131
{{{E(R-r)=e(R+r)}}}
{{{ER-Er=eR+er}}}
{{{er-Er=ER-eR}}}
{{{r(e-E)=R(E-e)}}}
{{{r=R((E-e)/(e-E))}}}
{{{r=-R((E-e)/(E-e))}}}
{{{r=-R}}}