Only B please

so far i tried subbing in r for Un but i have no idea how to do it

please show your step thank you

YEEEEEET Jan 10, 2019

#1

#3**+2 **

"*can you explain why you did Ur + U n+1 at the first part of ii please* "

Think of the summation as follows: \(\sum_{k=1}^nu_k=u_1+u_2+...+u_n\)

Hence \(\sum_{k=1}^{n+1}u_k=u_1+u_2+...+u_n+u_{n+1}\) which is \(\sum_{k=1}^{n+1}u_k=\sum_{k=1}^nu_k+u_{n+1}\)

Hope that makes it clear.

Alan
Jan 10, 2019