1 Calculeaza 2 pe 13 + 4 pe 13 + 6pe 13 + ...+104 pe 13=

5pe41 + 10pe41 + 15 pe41 =?


Răspuns :

2/13+4/13+6/13+...+104/13=
=(2+4+6+...+104)/13=
=2(1+2+3+...+52)/13=
=[(2×52×53)/2]/13=4×53=212


5/41+10/41+15/41=(5+10+15)/41=30/41