# MathWatch

#1
The common difference in an arithmetic sequence is 8 and the sum of the first 14 terms is 966, find the first term
0
1 week ago
#2
(Original post by ramthai)
The common difference in an arithmetic sequence is 8 and the sum of the first 14 terms is 966, find the first term
You need to do more than ask others to answer the question. The rules of this section do not allow for full solutions, only help.

Have you written an expression for the sum in terms of the difference and the first term? Please post your working.
0
1 week ago
#3
(Original post by ilikebigboottys)
The formula for the Arithmetic sequence is S = 1/2 n (2a+(n-1)d)
We know common difference d = 3
We know S = 966 when n = 14

So, we plug in the numbers we already have

966 = 1/2 14 (2a + (14-1)3)
966 = 7(2a + 39)

966 = 14a + 273
966-273 = 14a
693 = 14a
Therefore a (the first term) = 49.5

d = 8
0
1 week ago
#4
(Original post by moonlight98)
d = 8
oh chips, well u can just plug in 8 instead of 3 and still use the same method
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1 week ago
#5
(Original post by ilikebigboottys)
..
Please read the rules of this section - no full solutions. It's called "Study *Help*", not "We do your homework for you". The aim is to help people really understand how to tackle problems. I know that it's tempting to give the answer and move on, but it takes a more incremental approach to help students form their own understanding.
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