Partial Solutions For Extended Einsteinian Formulas:
  Additional Equations;

Solve For Ep,

       mc^2      E        1
E = --------- , ---- = --------
        mc^2    mc^2       mc^2
    1 + ----           1 + ---- ,
         Ep                 Ep

cross multiply,

         mc^2               mc^2    mc^2
E * (1 + ----) = mc^2,  1 + ---- =  ---- ,
          Ep                 Ep      E

mc^2    mc^2       mc^2    mc^2    E
---- =  ---- - 1,  ---- =  ---- -  -,
 Ep      E          Ep      E      E


mc^2    mc^2 - E
---- =  --------,
 Ep        E

cross multiply,

Ep * (mc^2 - E) = E * mc^2,

(equation #2):

      E * mc^2
Ep =  -------- .
      mc^2 - E