If $r = -1$, the infinite geometric series is $a - a + a - a + \ldots$, whose sum —

Question

Accepted Answer

does not exist

Answer

is $0$

Answer

is $a$

Answer

is $\dfrac{a}{2}$

If r=−1r = -1r=−1, the infinite geometric series is a−a+a−a+…a - a + a - a + \ldotsa−a+a−a+…, whose sum —