[填空题]
Only one of the following four sequencesml22m f2 tb 3g0oh6vem is arithmetic and only one ofll8f 2 f1ai2dd( 4pre bu+5 eofb x*1nsrr,b*w them is geometoi852 (br12sd p*+ re 1dlbxfebwlnr,fu f*a 4ric.
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.