First do only the part boxed in





Write  as 



Get the LCD of .  Multiply top and
bottom of  by 





Combine the numerators over the LCD:





Now go back to 


and replace the boxed-in part by 



Erasing the box:



Now do only the part boxed in here:





This can be done by inverting and multiplying:



Write  as :



Multiply numerators and denominators:



Now go back to



and replace the boxed-in part by 



Erasing the box:



Write  as 



Get the LCD of .  Multiply top and
bottom of  by 





Combine the numerators over the LCD:





Edwin