Answers

  • Brainly User
2014-02-28T12:41:29+05:30
 S_{n}= \frac{n(2a+(n-1)d)}{2}
n- number of terms
a-first term of the series
therfore
d=  \frac{\frac{2 S_{n}}{n}-2a}{n-1}= \frac{2 S_{n}-2an}{n(n-1)}
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