Question

rezolava exercitiul 1+2+3+.......409

Answer 1

1+2+3+.......409=409*410:2=83845

Answer 2

$Se \ foloseste \ formula \ lui \ Gauss \\ \\ \frac{n(n+1)}{1} \ unde \ n \ este \ ultimul \ numar \ din \ sir \ (409) \\ \\ \frac{409(409+1)}{2}= \frac{409*410}{2} = \frac{409*205}{1} =\boxed{83845\ raspuns \ final \ }$