Question

1+2+3+...+2019= ?
Dau coroana

Answer 1

$\underline{\textbf{Suma lui Gauss}}\\ 1+2+3+...+n = \dfrac{n\cdot(n+1)}{2}\\ \\ \\ \underline{\textbf{Rezolvare}}\\ 1+2+3+...+2019 = \dfrac{2019\cdot (2019+1)}{2} =\\ \\ =\dfrac{2019\cdot 2020}{2} = 2019\cdot 1010 =\boxed{2039190}$