# Doubt from sequence and series

#1
#2

If you have any doubt then ask me

#3
#4
#5
#6

Ques is for a/c not for a/b . So please recheck your ans.

#7

It's in GP so he can surely derive a/c

#8
#9

D will be 5 not -5

#10

As i think it is 5

#11

We have b-a=2(c-b)
If b=ar,c=ar^2 we have after substituting r-1=2r(r-1) \Rightarrow r=\dfrac{1}{2}

Hence \dfrac{a}{c} =4