If d be the common difference, then m S13=a4−a7+a10=a4−a7+a7+3 d=a7=213[a1+a13]=213[a1+a7+6d]=213[2a7]=13a7=13 m
If a1,a2,a3,…,an,…. are in A.P. such that a4−a7 +a10=m, then the sum of first 13 terms of this A.P., is :
Held on 23 Apr 2013 · Verified 6 Jul 2026.
10 m
12 m
13 m
15 m
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