Can you check my proof, (binomial theorem appplied)

[mr_coffee]

Hello everyone. The problem I'm wondering if I did correctly is #20. I also scanned #19 because that's a problem the book did which I know is correct.

Here is my work:
http://suprfile.com/src/1/438e7f6/lastscan.jpg


Thanks!

 

[mattmns]

Looks good.