JEE Main2013MathematicsSequences and SeriesActual
If a₁, a₂, a₃, , a_n, . are in A.P. such that a₄-a₇+a₁₀=m , then the sum of first 13 terms of this A.P., is :
Options
- A10 ~m
- B12 ~m
- C13 ~m
- D15 ~m
Correct answer
C. 13 ~m
Step-by-step solution
If d be the common difference, then aligned m & =a₄-a₇+a₁₀=a₄-a₇+a₇+3 ~d =a₇ ~S ₁₃ & = 13 2 [a₁+a₁₃ ]= 13 2 [a₁+a₇+6 d ] & = 13 2 [2 a₇ ]=13 a₇=13 ~m aligned