∞
Σ (d/2)(1/2) ^ n-1
n=1
sum_(n=1)^∞ 1/2 d (1/2)^(n - 1) = d
By the geometric series test, the series converges to d.
because n=1 the answer would be 1 because 1-1=0 and anything to the power of 0=1.
