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determină x din:
7×x+14×x+21×x+28×x+......+126×x=7×9×19
am nevoie rapid


Răspuns :

7×x+14×x+21×x+28×x+...+126×x=7×9×19

dam factor comun 7×x
7×x(1 + 2 + 3 + 4 +...+ 18) = 7 × 9 × 19

paranteza o calculam cu Suma lui Gauss
7×x × 18 × 19 : 2 = 7 × 9 × 19

7×x × 9 × 19 = 7 × 9 × 19

x = (7×9×19) : (7 × 9 × 19)

x = 1