mg=[tex]\sqrt{(7/\sqrt{7}) ^{3}*(7/\sqrt{7} )^{5} }[/tex] (raționalizăm)= [tex]\sqrt{(\sqrt{7}) ^{3}*(\sqrt{7}) ^{5}}[/tex] = [tex]7\sqrt{7}[/tex] ×[tex]49\sqrt{7}[/tex]= 343×7=2401, 2401 ∈ N
