[Đại 7] Violympic

N

nguyenbahiep1

$P = (-1)^{\frac{n(n+1)}{2}} \\ \\ n = 2013 \Rightarrow 2013(2014):2 = 2013.1007- số -lẻ \Rightarrow P(2013) = - 1 \\ \\ n = 2014 \Rightarrow 2014(2015):2 là-số-lẻ \Rightarrow P(2014) = - 1 \\ \\ \Rightarrow P(2013)+P(2014) = - 2 $
 
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