a: Khi x=4 thì \(A=\dfrac{4-2\cdot2}{4-1}=0\)
b: \(A=\dfrac{x-1-4\sqrt{x}+4+1}{x-1}=\dfrac{x-4\sqrt{x}+4}{x-1}=\dfrac{\left(\sqrt{x}-2\right)^2}{x-1}\)
c: P=A:B
\(=\dfrac{\left(\sqrt{x}-2\right)^2}{x-1}:\dfrac{x-2\sqrt{x}}{x-1}\)
\(=\dfrac{\left(\sqrt{x}-2\right)^2}{\sqrt{x}\left(\sqrt{x}-2\right)}=\dfrac{\sqrt{x}-2}{\sqrt{x}}\)
P=1/2
=>(căn x-2)/căn x=1/2
=>2căn x-4=căn x
=>căn x=4
=>x=16
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