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Cat face 1+3+5+...+73 varog ca ma grabes

Răspuns :

Seamana cu 1+3+5+...+2k-1 = k²

unde k reprezinta numarul termenilor !

In cazul sumei de mai sus ultimul termen este 2k-1=73

                                                                   adica: 2k=73+1

                                                                             k=74:2=37 !!!

=> S=1+3+5+...+73=37² = 1369 .