SOLUTION: if S2 = 10, S10 = 2 then what is a1, d (Arithmetic Sequence)

Question 1092278: if S2 = 10, S10 = 2 then what is a1, d (Arithmetic Sequence)
Answer by greenestamps(13200) (Show Source): You can put this solution on YOUR website!

Using a for the first term and d for the common difference...

S(2) = a + (a+d) = 2a+d = 10

S(10) = a + (a+d) + (a+2d) + ... + (a+9d) = 10a+45d

So we know

Multiply the first equation by 5 and subtract the second equation to eliminate variable a, then solve for d.

The common difference, d, is -1.2. Plug this value into one of the earlier equations to solve for a.

The first term, a is 5.6.

Answers: first term is 5.6; common difference is -1.2.
RELATED QUESTIONS
if SS2 = 10, S10 = 2 then what is a1, d (Arithmetic... (answered by ikleyn)

if S10 = 50, S50 = 0 then what is a10, S100 (Arithmetic... (answered by greenestamps)

ARITHMETIC SERIES - Sn=n/2(a1 + an) Find the sum of the terms of the following... (answered by Edwin McCravy)

What is the 15th term of the arithmetic sequence with a1 =10 and d=... (answered by ewatrrr)

What is the 25th term of the arithmetic sequence with a1= -1 and d= -10 (answered by richwmiller)

in an arithmetic sequence, what is d if a1 is 13 and a71 is... (answered by ewatrrr)

If a1 = 4 and d = -2 what are the first four terms of the arithmetic... (answered by Fombitz)

if S10 = 50, S50 = then what is a10, S100 (Geometric Sequence) (answered by ikleyn)

if S10 = 50, S50 = 0 then what is a10, S100 (Geometric Sequence) (answered by greenestamps)