Looks good to me!
This is the last identity, in this exercise.
I seem to have proved it, but I would appreciate someone checking my work to make sure that I havent got there by accident.
Multiplying the numerator and denominator by and gets me to:
, which gives:
Multiplying numerator and denominator by gives:
Thanks again. It's enormously helpful, there's nothing like that in any of my books.