Question

Determinati numerele de forma ab23 divizibile cu 9!!!

Answer 1

ab23-multiplu de 9;
⇒a+b+2+3
⇒a+b+5-multiplu de 9
⇒a+b+5=9⇒a+b=4⇒a,b∈[[1,3],[2,2],[3,1],[4,0];
⇒a+b+5=18⇒a+b=13⇒a,b∈[[4,9],[5,8],[6,7],[7,6],[8,5],[9,4]];
⇒numerele formate sunt:1323,2223,3123,4023,4923,5823,6723,7623,8523 si 9423;