Question

In an AP, if s5+s7= 167 and s10= 235, then find the AP, where Sn denotes the sum of

its first n terms.

Answer 1

the series is 1,6,11,16,........

Answer 2

Answer:

S5+S7=5/2(2a+4d) +7/2(2a+6d)=167

=5a+10d+7a+21d=167

=12a+31d=167   [let this be eqn 1]

similarly,

from S10=235, we get 2a+9d=47 {let this be equation 2}

by solving eqn 1 and 2, we get a=1 and d=5

therefore the ap is 1,6,11........

Step-by-step explanation: