# Fill in the gaps in this arithmetic sequence: -3,_,_,_,_,_,12

1
by sophia2

2015-07-19T13:33:23+08:00

Formula in finding terms in an arithmetic progression is

An = A1 +(n-1)d

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You are given that:

An = A7 = 12

A1 = -3

n = 7

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get the value of 'd' or the common difference to find the other terms

An = A1 + (n-1) d

12 = -3 + (7-1) d

12 = -3 + 6d

12 + 3 = 6d

15 = 6d

d = 15/6

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Using d you'll have the other terms

A2 = A1 + (n-1)d

A2 = -3 + (2-1)15/6

A2 = -3 + 15/6

A2 = -1/2

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A3 = A1 + (n-1)d

A3 = -3 + (3-1) 15/6

A3 = 2

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A4 = A1 + (n-1)d

A4 = -3 + (4-1) 15/6

A4 = 9/2

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A5 = A1 + (n-1) d

A5 = -3 + (5-1) 15/6

A5 = 7

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A6 = A1 +  (n-1) d

A6 = -3 + (6-1) 15/6

A6 = 19/2

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try to solve using that and you'll have the same answer
pls answer this 1,1 1/4,1 1/2,.....,9 3/4 find n
ask this as another question. kinda hard to type the answer in a comment box
sure wait
okey na