CBSE Class 10 Answered
Sum of the first n terms of AP is 3n^2/2 + 13n/2. Find the nth term of the AP (Substitution method not allowed)
Asked by manasvi.gopani | 18 Feb, 2018, 16:40: PM
![begin mathsize 16px style straight S subscript straight n equals fraction numerator 3 straight n squared over denominator 2 end fraction plus fraction numerator 13 straight n over denominator 2 end fraction
rightwards double arrow straight S subscript straight n minus 1 end subscript equals fraction numerator 3 left parenthesis straight n minus 1 right parenthesis squared over denominator 2 end fraction plus fraction numerator 13 left parenthesis straight n minus 1 right parenthesis over denominator 2 end fraction
rightwards double arrow straight S subscript straight n minus straight S subscript straight n minus 1 end subscript equals open square brackets fraction numerator 3 straight n squared over denominator 2 end fraction plus fraction numerator 13 straight n over denominator 2 end fraction close square brackets minus open square brackets fraction numerator 3 left parenthesis straight n minus 1 right parenthesis squared over denominator 2 end fraction plus fraction numerator 13 left parenthesis straight n minus 1 right parenthesis over denominator 2 end fraction close square brackets
rightwards double arrow straight a subscript straight n equals 3 over 2 open square brackets straight n squared minus left parenthesis straight n minus 1 right parenthesis squared close square brackets plus 13 over 2 open square brackets straight n minus left parenthesis straight n minus 1 right parenthesis close square brackets
rightwards double arrow straight a subscript straight n equals 3 over 2 left parenthesis 2 straight n minus 1 right parenthesis plus 13 over 2 end style](https://images.topperlearning.com/topper/tinymce/cache/a3300e7b1ef66695643b467e53a42d55.png)
Answered by Rashmi Khot | 18 Feb, 2018, 18:51: PM
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