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(x+1)+(x+2)+...+(x+4)=40x + 860

Răspuns :

(x+1)+(x+2)+...+(x+41) = 40x + 860

41x + (1+2+...+41) = 40x + 860

41x - 40x = 860 - 41*42:2

x  = 860 - 861 

x = - 1