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1+2+3+.............+124=?

Răspuns :

   

[tex]\displaystyle\\

1+2+3+...+124=\frac{124(124+1)}{2}=62\times125=\boxed{\bf 7750}[/tex]



n(n+1):2

unde n este ultimul termen adica 124

deci vine 124*125:2=15500:2=7750