Rút gọn biểu thức \(2y^2\sqrt{\dfrac{x^4}{4y^2}}\) với y<0

Rút gọn A=\(\left(\dfrac{3\sqrt{x}-7}{x-\sqrt{x}-6}-\dfrac{3\sqrt{x}-6}{x-4}+\dfrac{1}{\sqrt{x}-3}\right):\dfrac{\sqrt{x}+2}{x+4\sqrt{x}+4}\) với x≥0 ; x≠4 ; x≠9

Rút gọn 

P=\(\left(\dfrac{\sqrt{a}+1}{\sqrt{a}-1}-\dfrac{\sqrt{a}-1}{\sqrt{a}+1}+4\sqrt{a}\right)\dfrac{1}{2a\sqrt{a}}\) với a>0 ; a≠1

Rút gọn biểu thức

A=\(\dfrac{1-x}{x+\sqrt{x}-2}+\dfrac{\sqrt{x}-2}{\sqrt{x}+2}+\)\(\dfrac{\sqrt{x}-2}{\sqrt{x}+2}.\left(1+\dfrac{4}{\sqrt[]{x}-2}\right)\) với x≥0 ; x≠1 ; x≠4

Rút gọn A=\(\dfrac{6xy^2}{x^2-y^2}\sqrt{\dfrac{x^2-2xy+y^2}{9x^2y^4}}\)với x<y<0

1.Luis asked Robert :"Where does Sarah lived ?"

➝Luis asked Robert

2.Mary:"Did you swim last night?"

➝Mary asked me

3.Paul:"How many pencils have you gotten?"

➝Paul asked me

Cho C=\(\left(\dfrac{1}{1-\sqrt{a}}+\dfrac{1}{1+\sqrt{a}}\right):\left(\dfrac{1}{1-\sqrt{a}}-\dfrac{1}{1+\sqrt{a}}\right)+\)\(\dfrac{1}{1-\sqrt{a}}\)

a) Rút gọn C

b) Tìm a để C >0