Question

Gpt: \(\sqrt{\frac{1-2x}{x}}=\frac{3x+x^2}{x^2+1}\)

Answer 1

\(ĐKXĐ:\hept{\begin{cases}\frac{1-2x}{x}\ge0\\x\ne0\end{cases}\Leftrightarrow\hept{\begin{cases}x\left(1-2x\right)\ge0\\x\ne0\end{cases}\Leftrightarrow}}0< x\le\frac{1}{2}\)

Do \(x\ne0\)nên pt đã cho trở thành

\(\sqrt{\frac{1}{x}-2}=\frac{\frac{3}{x}+1}{1+\frac{1}{x^2}}\)

Đặt \(\frac{1}{x}=a\)kết hợp ĐKXĐ được \(a>2\)

Thu được pt \(\sqrt{a-2}=\frac{3a+1}{1+a^2}\)

\(\Leftrightarrow\left(1+a^2\right)\sqrt{a-2}=3a+1\)

\(\Leftrightarrow\left(1+a^2\right)\left(\sqrt{a-2}-1\right)=3a+1-a^2-1\)

\(\Leftrightarrow\left(a^2+1\right).\frac{a-3}{\sqrt{a-2}+1}=-a^2+3a\)

\(\Leftrightarrow\left(a-3\right)\left[\frac{a^2+1}{\sqrt{a-2}+1}+a\right]=0\)

Vì a > 2 nên [...] > 0 

Nên a = 3

<=> x = 1/3