a) `ĐKXĐ: x≥0`
`\sqrt(x^2+x+1/4)=x`
`⇔\sqrt[(x+1/2)^2]=x`
`⇔|x+1/2|=x`
\(⇔\left[ \begin{array}{l}x+\dfrac{1}{2}=x\\x+\dfrac{1}{2}=-x\end{array} \right.\)
\(⇔\left[ \begin{array}{l}x\in ∅\\x=\dfrac{-1}{4}(l)\end{array} \right.\)
b) `ĐKXĐ: x\in RR`
`\sqrt(9x^2+6x+1)=\sqrt(11-6\sqrt2`
`⇔\sqrt[(3x+1)^2]=\sqrt[(3-\sqrt2)^2]`
`⇔|3x+1|=3-\sqrt2`
\(⇔\left[ \begin{array}{l}3x+1=3-\sqrt2\\3x+1=\sqrt2-3\end{array} \right.\)
\(⇔\left[ \begin{array}{l}x=\dfrac{2-\sqrt2}{3}\\x=\dfrac{\sqrt2-4}{3}\end{array} \right.\)
