Evaluate the sum

Question

∑3 =0 (-1)k × 2k-1/2k-1
6

Answer 1

surely (2k-1)/(2k-1) = 1

So, the sum is

6
∑ (-1)^k = (-1)^3 + (-1)^4 + (-1)^5 + (-1)^6 = -1+1-1+1 = 0
3