.
The sum in the left side is equal to the sum of terms from i = 1 to i = N,
which is the same as the sum of terms from i = 1 to i = N,
which in turn is the difference A - B, where
A = sum from i= 1 to i=N, (1)
and
B = sum from i= 1 to i=N. (2)
Regarding the sum (1) see the lesson
- Mathematical induction for sequences other than arithmetic or geometric
in this site.
Regarding the sum (2) see the lesson
- Mathematical induction and arithmetic progressions
in this site.
Also, you have this free of charge online textbook in ALGEBRA-II in this site
- ALGEBRA-II - YOUR ONLINE TEXTBOOK.
The referred lessons are the part of this online textbook under the topic "Method of Mathematical induction".