f = first term , d = difference
f + 4d = 6 ... 12f + 48d = 72
12f + 66d = 45
18d = -27
The fifth term of an arithmetic sequence is equal to 6 and the sum of the first 12 terms is equal to 45. Find the first term and the common difference.
having trouble with this, can't figure out the steps?
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