daca nr [tex] 2^{2015} [/tex] are A cifre inseamna ca [tex]10^{A-1}\ \textless \ 2^{2015}\ \textless \ 10^{A}[/tex]
Analog [tex]10^{B-1}\ \textless \ 5^{2015}\ \textless \ 10^{B} \\ [/tex]
Inmultim relatiile si avem:
[tex] 10^{A+B-2} \ \textless \ 10^{2015} \ \textless \ 10^{A+B} [/tex]
Deci 2015= A+B-1, A+B=2016
