#### Answer

5

#### Work Step by Step

$S_{n}=\dfrac {a_{1}+a_{n}}{2}\times n\Rightarrow a_{1}=\dfrac {2S_{n}}{n}-a_{n}\Rightarrow a_{1}=\dfrac {2\times S_{16}}{16}-a_{16}=\dfrac {2\times \left( -160\right) }{16}=\left( -25\right) =5$

Published by
Pearson

ISBN 10:
013421742X

ISBN 13:
978-0-13421-742-0

5

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