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cum calculez 5+8+11+...........+305??




Răspuns :

5= 2 +3·1

8 =2+3·2

11=2+3·3

................

305= 2+3·101      ⇒    S = 2·101 + 3(1+2+3+...............+101) = =202+3·101·102/2= 202+15453=15665