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x+(x+1)+(x+2)+...+(x+30)=620

Răspuns :

X+(x+1)+(x+2)+...+(x+30)=620
31x+1+2+...+30=620
31x+30*31/2=620
31x+465=620
31x=620-465
31x=155
x=5

31x+(1+2+...+30)=620

31x+30x31/2=620

31x+465=620

31x=155

x=5