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S=6+12+18.....+606.
Cine știe va rog.


Răspuns :

S=6+12+18+...+606 /:6
S:6=1+2+3+...+101
S:6=101×102:2
S:6=101×51
S:6=5151
S=858,5
S= 6•1+6•2+....+6•101
Dam factor comun 6:
S= 6•(1+2+....+101)
S= (6• 101•102) : 2
S= 30906