Rezolvati in N ecuatia
x+(x+1)+(x+2)+...+(x+11)=78

Explicație pas cu pas:
x+(x+1)+(x+2)+...+(x+11)=78
12x+1+2+...+11=78
12x+11(11+1)/2=78
12x=78-66
12x=12
x=1
Bafta!
[tex]\it x+(x+1)+(x+2)+\ ...\ +(x+11)=78 \Leftrightarrow12x+1+2+...+11=78\Leftrightarrow\\ \\ \Leftrightarrow12x+66=78|_{-66} \Leftrightarrow12x=12 \Leftrightarrow x=1[/tex]