Question

In an ap , if S5 + S7=167 and S10=235 then find the ap where Sn denotes the sum of its 1st n terms

Answer 1

S5=a+4d
S7=a+6d
S10=a+9d=235
S5+S7=167
therefore 2a+10d=167
and a+9d=235
from these 2 equations we get d=12.625
therefore the ap starts with 40.75 and continue s with a difference d=12.625

Answer 2

Answer:

Step-by-step explanation:

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........

hope this answer helped you