حل تشریحی سوال شماره 229 ریاضی و آمار 3 انسانی

$S_{16}=\frac{16}{2}(2\times 10+(16-1)\times 5)=\frac{16}{2}(20+15\times 5)=8(20+75)=8\times 95=760$

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روش دوم:

$a_{16}=10+(15)(5)=85\Rightarrow S_{16}=\frac{16}{2}(10+85)=8\times 95=760$

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