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If a_{1},a_{2},a_{3},.............,a_{n}....... are in A.P. such that a_{4}-a_{7}+a_{10}=m, then the sum of first 13 terms of this A.P. is:

Option: 1

10m


Option: 2

12m


Option: 3

13m


Option: 4

15m


Answers (1)

best_answer

\\a_4-a_7+a_{10}=m\\(a+3d)-(a+6d)+a+9d=m\\a+6d=m

\\Now,\,\,\,S_{n}=\frac {n}2[a+(n-1)d]\\\\S_{13}=\frac {13}2[2a+12d]=13(a+6d)=13m

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Riya

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