Thread: Text Book Error?

I'm back with another potential error in the textbook by Chandler/Bostock, Core Course for A Level. Last time it was my mistake, but this time I am more confused:

Page 594, Question 8

The sum of the first n terms of a series is given by Sn = n(3n-4). Show that the terms of the series are in arithmetic progression.

Can this be right?

The test book is correct. You need to prove that the under lying sequence whose sum is given by is in A.P. Did you try considering ?

Spoiler:

Given
. Consider
Similarly we have


So they are in A.P with where

Ok, I can see where I have got confused now. It's one of those horrible oversights that seems silly when you realise. Thanks.

The books appear error is a normal phenomenon, there is always some small problems.

Actually, to be fair to the book, both cases that I have questioned have turned out to be careless errors from me. I think that is also a normal phenomenon