Răspuns :
După formula n(n+1) toata asta supra 2-> 500(500+1) toata supra 2-< 500*501 supra 2.
250*501=125.250
[tex]\displaystyle 1+2+3+...+500= \frac{500(500+1)}{2} = \frac{500 \times 501}{2} = \frac{250500}{2} =125250[/tex]