[latex]left(cfrac{1}{sqrt{5}}-sqrt{3} ight)^2=left(cfrac{1}{sqrt{5}} ight)^2-2cdotcfrac{1}{sqrt{5}}cdotsqrt{3}+(sqrt{3})^2=cfrac{1}{5}-cfrac{2sqrt{3}}{sqrt{5}}+3=cfrac{16}{5}-cfrac{2sqrt{15}}{5}=cfrac{16-2sqrt{15}}{5}=3,2-0,4sqrt{15}[/latex]