P=
a,Rút gọn P
b,Tìm m để x thoả mãn: P=mx
+1
a) ĐK: $x>0;x\neq 4$
$P=\dfrac{\sqrt{x}-5\sqrt{x}+4}{\sqrt{x}(\sqrt{x}-2)}:\dfrac{x-4-x}{\sqrt{x}(\sqrt{x}-2)}=\dfrac{4-4\sqrt{x}}{-4}=\dfrac{-4(\sqrt{x}-1)}{-4}=\sqrt{x}-1$
b) $P=mx\sqrt{x}-2mx+1$
$\Leftrightarrow \sqrt{x}-1=mx\sqrt{x}-2mx+1=0
\\\Leftrightarrow mx\sqrt{x}-2mx-\sqrt{x}+2=0
\\\Leftrightarrow mx(\sqrt{x}-2)-(\sqrt{x}-2)=0
\\\Leftrightarrow (\sqrt{x}-2)(mx-1)=0
\\\Rightarrow \cdots$