Question

Sum of infinite sequences:

1 - 1 + 1 - 1 + 1 - 1 + 1 - 1 +...
= (1 - 1) + (1 - 1) + (1 - 1 ) +...
= 0 + 0 + 0 + 0 + 0...
= 0

or
1 + (-1 + 1) + (-1 + 1) + (-1 + 1) +...
= 1 + 0 + 0 + 0 + 0 + 0 +...
= 1

Lol how do I know which one is correct, or is there something I'm missing

Answer 1

this is a divergent series so you can't sum it algebraically

treat it as a geometric series w/ a1 = 1 and r = -1 and use the geometric sum formula