Find the sum.

1 − 1/2+1/4-1/8+....-1/512

1 answer

did you recognize the series as a geometric series with
a = 1 and r = -1/2 ??

If you are studying this topic you MUST know the formula for the sum of n terms

hint: how many terms are there ?
look at this patters
term(2) = -1/2 = -1/2^1
term(3) = 1/4 = +1/2^2
term(4) = -1/8 = -1/2^3
...
term(n) = -1/2^9
mmmmhhhh?