For the arithmetic progression 3, 7, 11,

MATHEMATICS · Single correct · A Level · Mathematics · Sequences and series · Sequences and series

Problem

For the arithmetic progression 3, 7, 11, \dots\, the sum of the first nn terms is 200. Which one of the following equations in nn must be solved to find the required value of nn? (a) 4n2+2n−200=04n^{2}+2n-200=0 (b) 2n2+3n−200=02n^{2}+3n-200=0 (c) 2n2+n−200=02n^{2}+n-200=0 (d) 2n2+n−100=02n^{2}+n-100=0

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