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1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20 = ?

19 puncte + coroana + inimă
E urgent!!​


Răspuns :

Răspuns:

[tex]1+2+3+...+n=\frac{n\cdot\left(n+1\right)}{2}=>\ 1+2+3+...+20=\frac{20\cdot21}{2}[/tex]=210