\(\left(\sqrt{7-2\sqrt{10}}-\sqrt{7+2\sqrt{10}}\right)^2\)
= \(\left(\sqrt{\left(\sqrt{5}\right)^2-2\sqrt{5.2}+\left(\sqrt{2}\right)^2}-\sqrt{\left(\sqrt{5}\right)^2+2\sqrt{5.2}+\left(\sqrt{2}\right)^2}\right)^2\)
= \(\left(\sqrt{\left(\sqrt{5}-\sqrt{2}\right)^2}-\sqrt{\left(\sqrt{5}+\sqrt{2}\right)^2}\right)^2\)
= \(\left(\sqrt{5}-\sqrt{2}-\sqrt{5}-\sqrt{2}\right)^2\)
= \(\left(-2\sqrt{2}\right)^2\)
= 8