Question 1128617
{{{ ((s^3 - r^3) / (9r^2 + 9rs + 9s^2))/ ((pr- ps - qr + qs) / (q^2 - p^2 )) }}} 


{{{ (((s - r) (r^2 + r s + s^2)) / 9(r^2 + rs + s^2))/ ((p(r- s) - q(r - s)) / ((q - p)(q+p) )) }}} 


{{{ (((s - r) cross((r^2 + r s + s^2))) / 9cross((r^2 + rs + s^2)))/ (((p - q)(r - s)) / ((q - p)(q+p) ))}}} 



{{{ (-(r - s)  / 9)/ ((-cross((q - p))(r - s)) / (cross((q - p))(q+p) )) }}} 


{{{ ((r - s)  / 9)/ ((r - s) / (q+p)) ) }}} 


{{{ (cross((r - s))1  / 9)/ (cross((r - s))1 / (q+p) )) }}} 


{{{ (1  / 9)/ (1 / (q+p) ) }}} 


{{{ (q+p)   / 9 }}}