Determina numarul natural X pentru care 7*X+14*X+21*X+28*X+...+126*X=7*9*19

Răspuns :

7*X+14*X+21*X+28*X+...+126*X=7*9*19

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

7x × 18 × 19 : 2 = 7 × 9 × 19

7x × 9 × 19 = 7 × 9 × 19

x = (7 × 9 × 19 ) :(7 × 9 × 19)

x = 1