\(\sqrt{4+\sqrt{10+2\sqrt{5}}}-\sqrt{4-\sqrt{10+2\sqrt{5}}}\Rightarrow x^2=4+\sqrt{10+2\sqrt{5}}+4-\sqrt{10+2\sqrt{5}}-2\sqrt{\left(4-\sqrt{10+2\sqrt{5}}\right)\left(4+\sqrt{10+2\sqrt{5}}\right)}=8-2\sqrt{6-2\sqrt{5}}=8-2\sqrt{\left(1-\sqrt{5}\right)^2}=8-2\left(\sqrt{5}-1\right)=10-2\sqrt{5}\Rightarrow x=\sqrt{10-2\sqrt{5}}\)