Question

cu suma lui Gaus:
11+18+25+....+214=
6+11+16+...96=
rapid daca se poate,merci! XD

Answer 1

11 + (11+1·7) + (11+2·7) +.......+(11+29·7) = 11·30+ 7(1+2+3+.......+29) =
= 11·30 + 7·29·30/2 = 15(22+203) = 15·225 = 3375
6+ (6+5·1) + (6+5·2) +........+(6+5·18) = 6·19 + 5(1+2+3+....+18) =
= 6·19 + 5·18·19/2 = 19(6+45) = 19·51 = 969