Đáp án+Giải thích các bước giải:
Với `x≥0;x\ne9`
`A=\sqrtx/(\sqrtx+3)`
`\to 2\sqrt{x}.A=1`
`⇔2\sqrt{x}.\sqrtx/(\sqrtx+3)=1`
`⇔(2x)/(\sqrtx+3)=1`
`⇔2x=\sqrtx+3`
`⇔2x-\sqrtx-3=0`
`⇔2x+2\sqrtx-3\sqrtx-3=0`
`⇔2\sqrtx(\sqrtx+1)-3(\sqrtx+1)=0`
`⇔(\sqrtx+1)(2\sqrtx-3)=0`
\(⇔\left[ \begin{array}{l}\sqrt x+1=0\\2\sqrt x-3=0\end{array} \right.\)
\(⇔\left[ \begin{array}{l}\sqrt x=-1 \text{(Không thoả mãn)}\\\sqrt x=\dfrac{3}{2}\end{array} \right.\)
`⇔\sqrtx=3/2`
`⇔x=9/4(TM)`
Vậy `x=9/4` để `2\sqrt{x}.A=1`
