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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