Question

Cum se rezolva ex. urmat. 1+2+3+....+1199+1200=

Answer 1

1200x(1200+1):2=
=600x1201=
=720600

Answer 2

$\displaystyle 1+2+3+...+1199+1200= \frac{1200(1200+1)}{2} = \\ \\ = \frac{1200 \cdot 1201}{2} = \frac{1441200}{2} =720600$