Use the formula for the sum of a geometric series to find the sum or state that the series diverges.

Question

(4/9)^n starting at n=-4

Answer 1

well, you recall from Algebra II that

∞
∑ (4/9)^n = 1/(1 - 4/9) = 9/5
n=0

So just add on the first 4 terms from n = -4

Or, just start with a=(4/9)^-4 and use that in a/(1-r) for the sum