the common ratio is the number u multiply each term by to get to the next term
common ratio of 1/3
-9 * 1/3 = -9/3 = -3......so it is not the first one because the number after 9 in ur data is 3. not -3
-1/2 * 1/3 = -1/6....-1/6 * 1/3 = -1/18.....this is one...because if u keep multiplying by 1/3, it matches the data
900 * 1/3 = 900/3 = 300.....300 * 1/3 = 300/3 = 100...this is one as well
100 * 1/3 = 100/3 = 33.3...this is not one
so ur answers are : the 2nd and 3rd one
