Question 308469
Mutliply top and bottom by {{{xy}}}.
{{{ (x/y-y/x)/(1/y-1/x)= (xy(x/y-y/x))/(xy(1/y-1/x))}}}
{{{ (x/y-y/x)/(1/y-1/x)= (x^2-y^2)/(x-y)}}}
{{{ (x/y-y/x)/(1/y-1/x)= ((x+y)(x-y))/(x-y)}}}
{{{ (x/y-y/x)/(1/y-1/x)= ((x+y)cross(x-y))/cross(x-y)}}}
{{{ (x/y-y/x)/(1/y-1/x)= x+y}}}