U3 = ar\xb2, U6 = ar, , = , U6 -1, \xb2, = , ar^5 -1, , = r, -27, r = -, 3, U3 = ar\xb2, 27 = a, 9, ar, 243 -, ^{9} /tex, 3, , 81, mohon dicek kembali untuk hasil akhirnya, , U6/u3= ar^5/ar^2 = -1/27r^3=-1/27r=3221a-1/27r=-1/3cari a : ar^2 = 27a.(-1/3)^2 = 27a.1/9=27a=27.9a=243u10=ar^9=243.(-1/3)^9=243.(-1/19683)=-1/81