To the side let's calculate and simplify the most 
complicated part, the first term on top, which is 
:







Now we can substitute that into the right side of



for the 



And for  we just substitute 
 (enclosed in parentheses)

 

Remove the parentheses on top



Now every term on top will cancel except those which contain factor h:





Factor h out of the top:



Cancel the h's:





Edwin