Question

∑[k=1,4](-(1)/(3))^k find the indicted sum

Answer 1

(-(1)/(3))^1 + (-(1)/(3))^2 + (-(1)/(3))^3 = (-(1)/(3))^4
= -1/3 + 1/9 - 1/27 + 1/81 = -20/81 according to my calculator

Answer 2

Oops change that = in my first line to +