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x+(x+1)+(x+2) = 3 la puterea 21

Răspuns :

x+(x+1)+(x+2)=3^21
3x+3=3^21
x=(3^21-3):3
x=3^20-1
x+(x+1)+(x+2)=3^21; 3x+3=3^21; 3x=3^21-3; x=(3^21-3)/3=3^21/3-3/3=3^20-1