# math

The sum of the 1st nine terms of an arithmetic series is 216. The 1st,3rd and the 7th terms of series form the 1st three terms of a geometric series. Find the 1st term and the constant difference of the arithmetic series ?

1. 👍 0
2. 👎 0
3. 👁 561
1. just write what they told you:

9/2 (2a+8d) = 216
(a+2d)/(a) = (a+6d)/(a+2d)

Now solve for a and d.

Now, just for precision, you mean arithmetic sequence. A series is the sequence of partial sums of a sequence. For example,

sequence: 3,7,11,15,19,...
series: 3,10,21,36,55,...

1. 👍 0
2. 👎 0
2. The third term of an arithmetic sequence is 14 and the ninth term is -1 find the first four term of the sequence

1. 👍 0
2. 👎 0

## Similar Questions

1. ### Maths

The sum of 1st five terms of an AP nd the sum of the 1st seven termd of the same AP is 167. If the sum of the 1st ten terms of this AP is 235, find the sum of its1st twenty terms

2. ### Math

In an arithmetic series, the sum of the 5th to the 8th terms inclusive is 114, whilst the sum of the 12th to 15th terms inclusive is 198. What is the 21st term? I have got 99=2a +3d and 57= 2a+3d Im not sure what to do now

3. ### math

The sum of the first 5 terms of an arithmetic series is 70. The sum of the first 10 terms of this arithmetic series is 210. What is the first term of the series?

4. ### math

The sum of the first 20 terms of an arithmetic series is identical to the sum of the first 22 terms. If the common difference is -2, find the first term.

1. ### maths

the sum of the first nine terms of an arithmetic sequence 216. The 1st, 3rd and 7th terms form the first three terms of a geometric sequence therefore find the common difference

2. ### Math

In an arithmetic progression, the 5th term is six times the 1st term and the sum of the first six terms is 99. Find the 1st term and the common difference. Attempt at solution: U5 = 6(U1) 99 = 3(2[U1] + 2d)

3. ### Math:A.P.

The 1st,3rd and 9th terms of an A.P are the three terms of a G.P.if the 7th term of the A.P is 19.calculate the 20th term of the A.P and the sum of the first 12terms of the G.P(LEAVING YOUR ANSWER IN INDEX FORM)

4. ### Can someone help me?!

The 1st, 5th and 13th terms of an arithmetic sequence are the first three terms of a geometric sequence with a common ratio 2. If the 21st term of the arithmetic sequence is 72, calculate the sum of the first 10 terms of the

1. ### arithmetic

THE SUM OF THE 2ND AND 5TH TERMS OF AN A.P IS 42. IF THE DIFFERENCE BETWEEN THE 6TH AND 3RD TERM IS 12, FIND THE: COMMON DIFFERENCE, 1ST TERM, 20TH TERM.

2. ### mathematics

the 3rd term of an A.p is 9 while the 11th term is -7. Solve for the 1st five terms of the A.p

3. ### maths

a ball is dropped on the ground.The time interval between the 1st and 2nd bounce is 1.2s.The interval between the 1st and 2nd and 3rd bounce is 0.9s.Assume that successive time intevals form a geometric progression with an

4. ### Mathematics

A drinking straw of length 21 cm is cut into 3 pieces the length of the first piece is x cm the second piece is 3cm shorter than the 1st piece the third piece is twice as long as first piece (a) state in terms of x the length of