September 12, 2017

My Arthmetic Sequence

17,14,11,8,5…

$t_{n}=17+(n-1).(-3)$

$t_{n}=17-3n+3$

$t_{n}=-3n+20$

$t_{50}=17+(50-1).(-3)$

$t_{50}=17+49.(-3)$

$t_{50}=17-147$

$t_{50}=-130$

$S_{50}=\frac{50}{2}.[17+(-130)]$

$S_{50}=25.(-113)$

$S_{50}=-2825$

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