[tex]\displaystyle\bf\\f(x)=|x|\\\\f(\sqrt{5} )-f(-\sqrt{5} )+f(\sqrt{3} )=|\sqrt{5} |-|-\sqrt{5} |+|\sqrt{3} |=\\\\=\sqrt{5} -\sqrt{5} +\sqrt{3} =\sqrt{3} \\\\Otvet \ : \ \sqrt{3}[/tex]