(a)[2]
Determine the least value of $n$ for which the $n$th term is negative.
(b)[3]
It is stated that the sum of the first $2k$ terms of this progression is the same as the sum of the first $k$ terms. Determine the value of $k$.
Mathematics 9709 · AS & A Level · Series
Series — practice question
The initial term of an arithmetic progression is $84$, and its common difference is $-3$.