ab=10+a×b ; a,b=cifre; a diferit de 0
10a+b=10+a×b =>
•a=1 => 10+b=10+b => b=0,1,2,3,4,...,9 => ab=10,11,12,13,14,15,16,17,18,19
•a>1 => 10n+b=10+n×b. ; n=natural>1
10n-10=n×b-b => 10(n-1)=b(n-1)/:n-1
10=b
b= cifra => nu se poate => a=1
=> ab=10,11,12,13,14,15,16,17,18,19
Sper ca te-am ajutat!! :)))
