Write an expression for the gerneral or the nth term an for

Write an expression for the gerneral or the nth term an for the geometrci sequence.

2, 1, 1/2, 1/4, ...

A. 2 (1/2) n-1

B. 1 (1/2) n-1

C. 2 (1/4) n

D. 1 (1/3) n-1

Solution

common ratio , r = (1/2) = (1/2)/1 = (1/4)/(1/2) = 1/2

nth term of geometric sequenc : an = a1(r)^n-1

= 2(1/2)^(n-1)

Option A