Need help for Binomial!

Hi I need help with these questions on binomial theorem!

1.) From the binomial expansion of , deduce that



Using T( r+1) I know the coefficient of is . I had let n in be 2n+1 and x be 1.
That way, I got Is this wrong because from here, I do not know how to get

2.) By considering the binomial expansion of , find
I got as an answer for this one, I had just expanded out the summation and then let x=1. It's wrong..


Thank you so much!

Hey Tutu.

For 2) consider x = 2 instead of x = 1.

For 1) consider the binomial expansion (2 + 2)^n and how 4^n * [n]Cr gives [2n+1]Cr when you consider that adding all nCr's from 0 to n gives 2^n which means the square of this gives (2^n)^2 = 2^(2n) = (2^2)^n = 4^n.