$P=\dfrac{4\sqrt{x}+5}{\sqrt{x}-1}$ `(x≥0,x\ne1)`
Mà `P=4\sqrt{x}`
$⇔\dfrac{4\sqrt{x}+5}{\sqrt{x}-1}=4\sqrt{x}$
$⇔4\sqrt{x}+5=4\sqrt{x}(\sqrt{x}-1)$
$⇔4\sqrt{x}+5=4x-4\sqrt{x}$
$⇔4x-8\sqrt{x}-5=0$
$⇔4x+2\sqrt{x}-10\sqrt{x}-5=0$
$⇔(2\sqrt{x}-5)(2\sqrt{x}+1)=0$
$⇔2\sqrt{x}-5=0$ hoặc $2\sqrt{x}+1=0$
`⇔\sqrt{x}=5/2` hoặc `\sqrt{x}=-1/2`(loại)
`⇔x=(25)/4`(thỏa mãn)
Vậy `x=(25)/4`
