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calculati sumele a) 2+4+6+...+2014

Răspuns :

2(1+2+3+...+1007)=
=2(1007+1008:2)=
=2(1007+504)=
=2*1511=
=3022
2(1+2+3+...+1007)= 2(1007x1008):2=1007x1008