[填空题]
The third term, $u_{3}$ , of an arithmetic sequence is 7 . The common difference of the sequence, d , is 3 .
1. Find $u_{1}$ , the first term of the sequence.
2. Find $u_{60}$ , the 60 th term of sequence.
The first and fourth terms of this arithmetic sequence are the first two terms of a geometric sequence.
3. Calculate the sixth term of the geometric sequence.≈
