B=2√20+ √10 2 √(1-√5)

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a) \( B = 2\sqrt{20} + \frac{\sqrt{10}}{2} - \frac{\sqrt{(1-\sqrt{5})^2}}{} \)

b) \( C = \frac{2 - \sqrt{2}}{\sqrt{2} - 1} \)

c) \( D = \sqrt{3}(2\sqrt{3} - \sqrt{27 - 1}) \)