Answer
$-142$
Work Step by Step
$\left( a_{m}-a_{n}\right) =\left( m-n\right) d\Rightarrow a_{13}-a_{6}=\left( 13-6\right) d\Rightarrow 26-\left( -72\right) =7d=d=14;a_{6}=a_{1}+5d\Rightarrow -72=a_{1}+5\times 14\Rightarrow a_{1}=-142$
Precalculus (6th Edition)
by Lial, Margaret L.; Hornsby, John; Schneider, David I.; Daniels, Callie
Published by
Pearson
ISBN 10:
013421742X
ISBN 13:
978-0-13421-742-0
Chapter 11 - Further Topics in Algebra - 11.2 Arithmetic Sequences and Series - 11.2 Exercises - Page 1025: 36
Update this answer!
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.
