1.
\(A=\sqrt[3]{6\sqrt{3}+10}-\sqrt[3]{6\sqrt{3}-10}\)
\(=\sqrt[3]{\left(\sqrt{3}+1\right)^3}-\sqrt[3]{\left(\sqrt{3}-1\right)^3}\)
\(=\sqrt{3}+1-\sqrt{3}+1=2\)
2.
\(B=\sqrt{3+\sqrt{3}+\sqrt[3]{6\sqrt{3}+10}}\)
\(=\sqrt{3+\sqrt{3}+\sqrt[3]{\left(\sqrt{3}+1\right)^3}}\)
\(=\sqrt{3+\sqrt{3}+\sqrt{3}+1}\)
\(=\sqrt{4+2\sqrt{3}}\)
\(=\sqrt{\left(\sqrt{3}+1\right)^2}=\sqrt{3}+1\)
3.
\(C=\dfrac{2}{\sqrt[3]{3}-1}-\dfrac{4}{\sqrt[3]{9}-\sqrt[3]{3}+1}\)
\(=\dfrac{2\left(\sqrt[3]{9}-\sqrt[3]{3}+1\right)-4\left(\sqrt[3]{3}-1\right)}{\left(\sqrt[3]{3}-1\right)\left(\sqrt[3]{9}-\sqrt[3]{3}+1\right)}\)
\(=\dfrac{2\sqrt[3]{9}-2\sqrt[3]{3}+2-4\sqrt[3]{3}+4}{3-1}\)
\(=\sqrt[3]{9}-3\sqrt[3]{3}+3\)