ĐK: \(0\le x\le1\)
Đặt \(t=\sqrt{x}+\sqrt{1-x}\) ( \(t>0\) )
\(\Leftrightarrow t^2=x+1-x+2\sqrt{x\left(1-x\right)}\)
\(\Leftrightarrow t^2-1=2\sqrt{x-x^2}\)
\(\Leftrightarrow\frac{t^2-1}{2}=\sqrt{x-x^2}\)
Ta có \(pt\Leftrightarrow1+\frac{2}{3}\cdot\frac{t^2-1}{2}=t\)
\(\Leftrightarrow1+\frac{t^2-1}{3}-t=0\)
\(\Leftrightarrow t^2-1-3t+3=0\)
\(\Leftrightarrow t^2-3t+2=0\)
\(\Leftrightarrow\left(t-1\right)\left(t-2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}t=1\\t=2\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{x}+\sqrt{1-x}=1\\\sqrt{x}+\sqrt{1-x}=2\end{matrix}\right.\)
TH1: \(\sqrt{x}+\sqrt{1-x}=1\)
\(\Leftrightarrow x+1-x+2\sqrt{x\left(1-x\right)}=1\)
\(\Leftrightarrow\sqrt{x\left(1-x\right)}=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=1\end{matrix}\right.\)( thỏa (
TH2: \(\sqrt{x}+\sqrt{1-x}=2\)
\(\Leftrightarrow x+1-x+2\sqrt{x\left(1-x\right)}=4\)
\(\Leftrightarrow\sqrt{x\left(1-x\right)}=\frac{3}{2}\)
\(\Leftrightarrow x\left(1-x\right)=\frac{9}{4}\)
\(\Leftrightarrow4x\left(1-x\right)=9\)
\(\Leftrightarrow4x^2-4x+9=0\)
\(\Leftrightarrow\left(2x+1\right)^2+8=0\)( vô lý )
Vậy \(x\in\left\{0;1\right\}\)
