#### Answer

$5=a_1$

#### Work Step by Step

The n th term of an arithmetic sequence can be calculated as:
$a_n=a_1+d\times(n-1)$
Here: $a_{8}=33$, $d=4$ and we have to find $a_{1}$.
By substituting we get:
$33=a_1+4\times(8-1)$
$33-28=5=a_1$

Published by
Pearson

ISBN 10:
0-32184-874-8

ISBN 13:
978-0-32184-874-1

$5=a_1$

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