Question

Determinati toate numerele naturale abc ,stiind ca a+b=8 si c=3xbl

Answer 1

a+b=8⇒a,b∈[[1,7],[2,6],[3,5],[4,4],[5,3],[6,2],[7,1]];
⇒c=3b⇔c∈[21,18,15,12,9,6,3]⇒c-este cifra⇒c∉[21,18,15,12]⇒c∈[9,6,3];
⇒din observatia de mai sus⇒b∉[7,6,5,4]⇒b∈[3,2,1] ,acelasi caz pentru a∉[1,2,3,4]⇒a∈[5,6,7];
⇒numerele formate sunt:539,626,713;