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1+2+3...+80
Cum se face ajutati-ma


Răspuns :

(80*81):2
40*81
=3240

* = ori
Cu placere.
[tex]\displaystyle 1+2+3+...+80= \frac{80(80+1)}{2} = \frac{80 \times 81}{2} = \frac{6480}{2} =3240[/tex]