For an arithmetic progression the first term is 7 and the common difference is 3
MATHEMATICS · Subjective · A Level · Mathematics · Sequences and series · Sequences and series
Problem
For an arithmetic progression the first term is 7 and the common difference is 3. The sum of the first n terms equals three times the sum of the first eight terms.
(a) Form an equation in n that represents the given condition.
(b) Solve the equation to find the value of n.
(c) Using the value of n obtained in part (b), calculate the sum of the terms from the 9th to the nth term inclusive.