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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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