Math, asked by shaikasifahamed5688, 10 months ago

If the sum of first 3rd term of an ap is 9 and that of 13th term is 169 find the common difference and also sum of first n terms

Answers

Answered by shivk32211223

Answer:

S3=3/2{2a+(3-1)d=9 and S13=13/2{2a+(13-1)d=169 or 3/2{2a+2d}=9 and 13/2{2a+12d}=169 or 2a+2d=9×2/3=6 and 2a+12d=169×2/13=26 aubstracting -10d=-20 or d=20/10=2 ....so cd is 2. now Sn=n/2{2a+(n-1)2}..(putting d=2)

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