\(\left(\dfrac{14}{\sqrt{14}}+\dfrac{\sqrt{12}+\sqrt{30}}{\sqrt{2}+\sqrt{5}}\right).\sqrt{5-\sqrt{21}}=4\)

chứng minh VT

\(\dfrac{4}{3+\sqrt{5}}-\dfrac{8}{1+\sqrt{5}}+\dfrac{15}{\sqrt{5}}\)

tính

\(\dfrac{1}{2\sqrt{2}}-\dfrac{3}{2}\sqrt{4.5}+\dfrac{2}{5}\sqrt{50}\)

tính

M=\(\left(\dfrac{\sqrt{x}}{\sqrt{x}-2}+\dfrac{\sqrt{x}}{\sqrt{x}+2}\right).\dfrac{x-4}{\sqrt{4x}}\)

a, tìm ĐK

b,Rút gọn

c,Tìm x để M=3

\(\dfrac{\sqrt{a}+1}{a\sqrt{a}+a+\sqrt{a}}:\dfrac{1}{a^2-\sqrt{a}}\)

rút gọn

\(\dfrac{a+b-2\sqrt{ab}}{\sqrt{a}-\sqrt{b}}-\dfrac{a-b}{\sqrt{a}+\sqrt{b}}\)

rút gọn

\(\dfrac{3}{2}\sqrt{3x}-\sqrt{3x}-5=\dfrac{1}{2}\sqrt{3x}\)

tìm x