Bài 1 : Thực hiện phép tính , rút gọn biểu thức

A = (\(\sqrt{5}\)-2)(\(\sqrt{5}\)+2)

B = (\(\sqrt{5}\) +\(\sqrt{3}\))(5-\(\sqrt{15}\))

C = (\(\sqrt{45}+\sqrt{63}\))(\(\sqrt{7}-\sqrt{5}\))

D = \(\dfrac{1}{\sqrt{3}+1}+\dfrac{1}{\sqrt{3}-1}\)

E = \(\dfrac{5+\sqrt{5}}{5-\sqrt{5}}+\dfrac{5-\sqrt{5}}{5+\sqrt{5}}\)

F = \(\dfrac{\sqrt{3}}{\sqrt{\sqrt{3}+1}-1}-\dfrac{\sqrt{3}}{\sqrt{\sqrt{3}+1}+1}\)

G = \(\sqrt{\left(2-\sqrt{3}\right)^2}+\sqrt{4-2\sqrt{3}}\)

H = \(\sqrt{2-\sqrt{3}}-\sqrt{2+\sqrt{3}}\)

I = \(\sqrt{\dfrac{3-\sqrt{5}}{3+\sqrt{5}}}-\sqrt{\dfrac{3+\sqrt{5}}{3-\sqrt{5}}}\)

K = \(\sqrt{3+\sqrt{5}}+\sqrt{7-3\sqrt{5}}-\sqrt{2}\)