Hi I've some more questions, your help is greatly appreciated!

1.) and the sum of it's coefficients is 1, what is the sum of the coefficients of

I really have no idea how to start, can't see any patterns..

2a.) Prove that

I did this ok so ignore this part! I had just typed it down as this part may yield a clue for the other parts.

2b.) Hence show that

2c.) Suppose the numbers Pr ( r is a subscript!) are defined by

Prove that

and that

How do I do them! Please help me thank you so much!!!