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The first and the last term of ap is 21 and-47 ,if the sum of series is 234 calculate ,number of term ,common difference, thesum of first 18 terms

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S = n/2 (2a+d)
Plugging your numbers, I don't get a positive integer ...

my bad
S = n/2 (a1+an) = n/2 (21 + 47) = 234
Hmm. Still not a positive integer for n.

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