This is more difficult, I see familiar things (formulas basically behind numbers), but end with different result. How it is good to start simplifying it?

Expression:

Answer:

Things what I see:

Formula:

same thing with:

I am not sure about this one:

Going inside parenthesis:

Formula:

Common denominator in my opinion is:

Ready to divide (which is multiplication with opposite number):

I know it looks crazy.

I calculated it and got as final result:

Interesting, but when I set a = 1 my simplification and textbook answer give different results. I went wrong, tips how I should approach it?