The 6th term of an a.p is 35 and the 13th term is 77.calculate s6-s4

2 answers

Answer
a+5d = 35
a+12d = 77
find a and d, and then
S6-S4 = 6/2 (2a+5d) - 4/2 (2a+3d)
or, more simply, S6-S4 = a5+a6 = a+4d + a+5d = 2a+9d