a: \(A=\frac{1}{3-\sqrt{10}}-\frac{1}{3+\sqrt{10}}\)
\(=\frac{3+\sqrt{10}-\left(3-\sqrt{10}\right)}{\left(3-\sqrt{10}\right)\left(3+\sqrt{10}\right)}\)
\(=\frac{3+\sqrt{10}-3+\sqrt{10}}{9-10}=\frac{2\sqrt{10}}{-1}=-2\sqrt{10}\)
b: \(B=\sqrt{11-6\sqrt2}-\sqrt{11+6\sqrt2}\)
\(=\sqrt{\left(3-\sqrt2\right)^2}-\sqrt{\left.\left(\left.3+\sqrt2\right.\right)^2\right.}\)
\(=3-\sqrt2-3-\sqrt2=-2\sqrt2\)
c: \(C=\sqrt8-\sqrt{50}+\frac{3}{\sqrt2}\)
\(=2\sqrt2-5\sqrt2+\frac{3\sqrt2}{2}=-3\sqrt2+\frac32\sqrt2=-\frac32\sqrt2\)
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