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.
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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.
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
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
1 answer