Asked by Achire

The sum of the first 5 terms of an AP is 40 and the 7th term is equal to 4 times the second term, find the first term (a), common difference (d) and the sum of the second five terms.
Answered by Achire
4. The sum of the first 5 terms of an AP is 40 and the 7th term is equal to 4 times the second term, find the first term (a), common difference (d) and the sum of the second five terms.
Answered by Steve
why post it twice? Using your formulas, you see that

5/2 (2a+4d) = 40
a+6d = 4(a+d)

Now you can find a and d, and thus the sum of the 2nd five terms is the sum of the first 10, less the sum of the first 5:

10/2 (2a+9d) - 40
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