[填空题]
Only one of the following four sequen5/,xiq( ri nmhceqro41ecqrs8 2rf oo4l7,7jr bvdyv+ 8s is arithmetic and only one of them is geosv72ol4r bq8jr1c r, ryd+qovfeo784 metric.
1.State which sequence is arithmetic and find the common difference of the sequence.
Hence b$_n$ is arithmetic and d= .
2.State which sequence is geometric and find the common ratio of the sequence.
Hence C$_n$ is geometric and r= .
3.For the geometric sequence find the exact value of the sixth term. Give your answer as a fraction.
