\(\text{Câu 1 : }\\ \sqrt{\dfrac{4}{9}-\sqrt{\dfrac{25}{36}}}=\sqrt{\dfrac{4}{9}-\dfrac{5}{6}}=\sqrt{\dfrac{-7}{18}}\\ \text{Mà }-\dfrac{7}{18}< 0\\ \Rightarrow\text{ Biểu thức không có giá trị}\)

\(\text{Câu 2 :}\)

\(\text{a) }\left(x-1\right)^2=\dfrac{9}{16}\\ \Leftrightarrow\left(x-1\right)=\left(\dfrac{3}{4}\right)^2\\ \Leftrightarrow x-1=\dfrac{3}{4}\\ \Leftrightarrow x=\dfrac{7}{4}\\ \text{Vậy }x=\dfrac{7}{4}\)

\(\text{b) }x-2\sqrt{x}=0\\ \Leftrightarrow\sqrt{x}\left(\sqrt{x}-2\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}\sqrt{x}=0\\\sqrt{x}-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\\sqrt{x}=2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\sqrt{2}\end{matrix}\right.\\ \text{Vậy }x=0\text{ hoặc }x=\sqrt{2}\)

\(\text{c) }x=\sqrt{x}\\ \Leftrightarrow x-\sqrt{x}=0\\ \Leftrightarrow\sqrt{x}\left(\sqrt{x}-1\right)\\ \Leftrightarrow\left[{}\begin{matrix}\sqrt{x}=0\\\sqrt{x}-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\\sqrt{x}=1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=1\end{matrix}\right.\\ \text{Vậy }x=0\text{ hoặc }x=1\)