The sum of the first terms of a sequence is .

MATHEMATICS · Multi-part · CBSE · Mathematics · Arithmetic Progressions · Arithmetic Progressions

Problem

The sum of the first nn terms of a sequence is Sn=7n2−4nS_n = 7n^2 - 4n. (i) Show that the sequence is an arithmetic progression. (ii) Find its common difference. (iii) Calculate the 20th term.

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