Rút gọn

A=\(\dfrac{2}{x^2-y^2}.\sqrt{\dfrac{3y^2+6xy+3y^2}{4}}\)

B=\(\dfrac{1}{2a-1}.\sqrt{5a^4\left(1-4a+4a^2\right)}\)

Rút gọn

A=\(\sqrt{\left(x^2-4\right)}.\sqrt{\dfrac{9}{x^2-4x+4}}\) với \(x>2\)

B=\(\sqrt{\dfrac{8y^2}{x^2-9}}.\sqrt{\dfrac{\left(x-3\right)^2}{y^2}}\) với x<3,y>0

Tính

A=\(\sqrt{9-\sqrt{17}.}\sqrt{9+\sqrt{17}}\)

B=\(\sqrt{3+\sqrt{5+2\sqrt{3}}.}\sqrt{5-\sqrt{5+2\sqrt{3}}}\)

Tính 

A=\(\sqrt{49}.\sqrt{144}+\sqrt{257}:\sqrt{64}\)

B=\(\left(\sqrt{12}+\sqrt{75}+\sqrt{27}\right):\sqrt{15}\)

C=\(\left(\sqrt{\dfrac{1}{7}}-\sqrt{\dfrac{16}{7}}+\sqrt{\dfrac{9}{7}}\right):\sqrt{7}\)