Question 309888
{{{(r^2-s^2)/(s-r)=-(r^2-s^2)/(r-s)=-((r+s)(r-s))/(r-s)=-((r+s)*cross((r-s)))/cross((r-s))=-(r+s)=-r-s}}}



So {{{(r^2-s^2)/(s-r)=-r-s}}}