Răspuns :
[tex]\it \dfrac{5\sqrt2+1}{x}= \dfrac{7}{5\sqrt2-1} \Rightarrow x= \dfrac{(5\sqrt2-1)(5\sqrt2+1)}{7}= \dfrac{50-1}{7}= \dfrac{49}{7}=7[/tex]
[tex]\it \dfrac{5\sqrt2+1}{x}= \dfrac{7}{5\sqrt2-1} \Rightarrow x= \dfrac{(5\sqrt2-1)(5\sqrt2+1)}{7}= \dfrac{50-1}{7}= \dfrac{49}{7}=7[/tex]