Question

Chỉ cần làm bài 8,9 ( trc 21h )thôi cảm ơn 

Answer 1

8:

a: \(P=\dfrac{x+4-x-4\sqrt{x}-4}{\sqrt{x}\left(\sqrt{x}+2\right)}:\dfrac{2\sqrt{x}-4}{\sqrt{x}\left(\sqrt{x}-2\right)}\)

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

b: Khi x=9-4căn 5 thì \(P=\dfrac{-2\left(\sqrt{5}-2\right)}{11-4\sqrt{5}}\)

c: P>-1

=>P+1>0

=>x+2-2căn x>0(luôn đúng)