Question

In an A.P., if S5 + S7 = 167 and S10 = 235, then find the A.P.

Answer 1

First of all you will find the first term
Tn=a(n-1)d
and put the and use the formula of Sn =n/2[2a +(n -1 )d]

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: