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Imi poate spune cineva cum se rezolva b=1+6++11+16+...+2016 si explicatia?

Răspuns :

6=1+5; 11=1+2*5; 16=1+3*5

b=1+ 1+5 + 1+2*5 + 1+3*5 +...+ 403*5+1 = (1+2016)*404/2=2017*202=407434
b = 1+6+11+16+....+2016 = 1+1+5+1+10+1+15+....+1+2015 = 1x404 + (5+10+15+...+2015) = 404 + 5(1+2+3+4+...+403) = 404+5*404*403/2 = 404+5*202*403 = 407434