if four arithmetic means are inserted between-21 and -1, find the first of these arithmetic means
A. - 17
B. -13
C.-9
D.-5

a gardener makes a triangular planting with 40 plants in the front row, 36 in the second row. 32 in the third row, and so on. If there are 7 rows, how many plants are there in all?
A. 196
B. 244
c. 364
D. 392

the sum of the first 10 terms of an arithmetic sequence is 530. What is the first term if the last ferm is 80?
A.5
B. -5
C.-26
D.26

If the general term of an arithmetic sequence is a n = 7 - 3n, find the sum of the first 7 terms of sequence.
A. -56
B. -35
C. 35
D. 56

find the missing term in the given arithmetic sequence 4, 9, 14, _, _, 29,34.
A. 18 & 22
B. 9 & 22
C. 19 & 24
D. 19 & 23​