Question

Calculeazā:
37+43+49+...+115=?
Repede vā rog,dau coroana!!

Answer 1

Explicație pas cu pas:

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Answer 2

$\displaystyle S = 37+43+49+...+115 = \sum\limits_{k=1}^{n}(6k+31) \\ \\ 6n+31 = 115 \Rightarrow 6n = 84 \Rightarrow n = 14 \\ \\ S = \sum\limits_{k=1}^{14}(6k+31) = 6\sum\limits_{k=1}^{14}k +\sum\limits_{k=1}^{14} 31 = \\ \\ \\=6\cdot \dfrac{14\cdot 15}{2}+31\cdot 14 = 3\cdot 14\cdot 15+31\cdot 14 =\boxed{1064}$