The 12th term of an arithmetic sequence,

MATHEMATICS · Multi-part · A Level · Mathematics · Sequences and series · Sequences and series

Problem

The 12^th term of an arithmetic sequence,

a_{12}

, is twice as large as the 4^th term in the sequence,

a_4

. (1) Given

a_{14} = 27

, find the value of

a_1

. (2) Find the 20^th partial sum of this sequence.