\(\sqrt{14-8\sqrt{3}}-\sqrt{24-12\sqrt{3}}=\dfrac{\sqrt{16-2.4.2\sqrt{3}+12}-\sqrt{36-2.6.2\sqrt{3}+12}}{\sqrt{2}}=\dfrac{\sqrt{\left(4-2\sqrt{3}\right)^2}-\sqrt{\left(6-2\sqrt{3}\right)^2}}{\sqrt{2}}=\dfrac{4-2\sqrt{3}-6+2\sqrt{3}}{\sqrt{2}}=\dfrac{-2}{\sqrt{2}}=-\sqrt{2}\)