👤

1+2+3+4+...+1997+1998+1999=?

Răspuns :

1+2+3+4+....+1997+1998+1999=[(primul termen+ultimul termen) * numarul de termeni] / 2= [(1+1999) * 1999] / 2= 2000 * 1999 / 2 = 1000 * 1999 = 1999000