Question

Calculati suma tuturor nr naturale nenule care impartite la 78 dau catul egal cu restul

Answer 1

n:78=c rest r<78 c=r
n=78*c+r=78*c+c=79*c=79*r
r=0⇒n=0 imposibil
r=1⇒n=79
r=2⇒n=2*79
r=3⇒n3*79
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r=77⇒n=77*79

79+2*79+3*79+..+77*79=79*(1+2+3+..+77)=79*77*78:2=237237