Respuesta :

tonb
only three terms luckily:

8*(1/4)^0 + 8*(1/4)^1 + 8*(1/4)^2 =

8*(1 + 1/4 + 1/16) = 21/2, answer D.
Because this sum have only 3 terms, the easiest way would be just substitute values of i from  1 to 3, and then add all terms.

8(1/4)¹⁻¹ + 8(1/4)²⁻¹ + 8(1/4)³⁻¹ = 8*1 + 8*1/4 + 8*1/16= 8+2+1/2= 10+1/2 = 21/2

Answer is D. 21/2