[tex]\hbox{ Se cauta numarul a } \in \hbox{R care sa indeplineasca relatia:} \ \ \ \boxed{\boxed{x*a=a}}\\\\\\ax-x-a+2=a\\\\ax-2a-x+2=0\\\\ a(x-2)-(x-2)=0\\\\(x-2)(a-1)=0 \\\\\\ a-1=0 \ \ \ ===\ \textgreater \ \underline{\underline{a=1}} [/tex]
[tex]E= \underbrace{\frac{\sqrt{1}}{2}*\frac{\sqrt{2}}{2}*\frac{\sqrt{3}}{2}}_{m}*\frac{\sqrt{4}}{2}}*\underbrace{\frac{\sqrt{5}}{2}*...*\frac{\sqrt{2017}}{2}}_{n}\\\\\\ E=m * \frac{2}{2} *n[/tex]
[tex]E= \underbrace{\underbrace{m*1}_{1} *n}_{1} = 1 \\\\\\ \boxed{ \hbox{ R : B }}[/tex]
