what formula describes the sequence 50,25,12.5,6.25....?

Question

a) an=50(.5)^n

b) an= 25(.5)^n-1

c) an= 50(.5)^n-1

d) an= 50(2)^n-1

Answer 1

Assuming n ≥1

50(.5)⁰, 50(.5)¹, 50(.5)², .......,50(.5)^n-1

answer c

However if n≥0 then the answer is "a".