Răspuns :

Pai faci cu gauss suma de la 1 la 79 si e = (79*80)/2=3160
Si faci suma lui gauss pana la 23 = (22*23)/2=253 si apoi le scazi pe cele doua
3160-253=2907

 

[tex]\displaystyle\bf\\Formula~lui~Gauss~este:\\\\S=\frac{n(Ultimul + Primul)}{2}\\ unde~n=numarul~de~termeni\\\\n=79-23+1=56+1=57~termeni\\\\23+24+25+...+79=\frac{57(79+23)}{2}=\frac{57\times102}{2}=57\times51=\boxed{\bf2907}[/tex]

 

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