If a1, a2, a3,...., an,... are in A.P. such that a4-a7+a10=m, then sum of the first 13 terms of the A.P. is

Let d be the common difference of the A.P.,then       m=a4−a7+a10=a4+a10−a7   =a1+3d+3d=a1+6dNow,    S13=1322a1+(13−1)d=13m.