Question

Please help!
The second term of arithmetic sequence is 7. The sum of the first 4 terms of the arithmetic sequence is 12. Find the the first term a1, and tje common difference, d, of the sequence.

Answer 1

2nd term = a1 + d where a1 = first term and d = common difference

so we can write a + d = 7

Answer 2

* a1 + d

Answer 3

do you know the formula for the sum of n terms of an arithmetic sequence?

Answer 4

hmm. i'm talking to myself...

Answer 5

an= a1 + (n -1)d

Answer 6

Why not let n= {1, 2, 3, 4} and write out \[a _{n}=a _{1}+(n-1)d \]

Answer 7

for each of those n values? This might help you find the unknowns, which are \[a _{1}~and~r\]

... where a1 is the first term and r is the common difference (not common ratio).

Answer 8

Note that because the second term is 7, the formula given about would come out as follows for n=2 (2nd term):\[a _{2}=a _{1}+(2-1)d\]=7

Answer 9

Thus, \[a _{2}=7=a _{1}+(2-1)d\]

Answer 10

What do i do nxt? To find the first term?

Answer 11

This question needs attention. Its been long time I was dealing with these things

Answer 12

What must you do to "solve" this problem? What are your goals? If you can answer these questions, then perhaps "what to do next?" will be clearer.

Answer 13

@welshfella