+1−1+1−1+... Explained in 5 Levels from Algebra to Math Major

What is +1−1+1−1+...?  Let's explore this series in 5 levels, ranging from explorations with arithmetic and algebra to rigorous solutions from Calculus and beyond!

00:00 Introduction
00:18 Level 1 -- Arithmetic Ideas
01:33 Level 2 -- Algebra Ideas
03:01 Level 3 -- Calculus
04:01 Level 4 -- Cesàro Sum
05:20 Level 5 -- Abel Sum