Question

Giải giúp mình vs ạ 

Answer 1

Bài 4: 

a) ĐKXĐ: \(-3\le x\le3\)

b) ĐKXĐ: \(x^2-4>0\)

\(\Leftrightarrow\left[{}\begin{matrix}x>2\\x< -2\end{matrix}\right.\)

c) ĐKXĐ: \(\left\{{}\begin{matrix}x\ge0\\x\ne9\end{matrix}\right.\)

Answer 2

Bài 5: 

a) Ta có: \(\sqrt{\left(3-\sqrt{10}\right)^2}\)

\(=\left|3-\sqrt{10}\right|\)

\(=\sqrt{10}-3\)

b) Ta có: \(\sqrt{9-4\sqrt{5}}\)

\(=\sqrt{\left(\sqrt{5}-2\right)^2}\)

\(=\sqrt{5}-2\)

c) Ta có: \(3x-\sqrt{x^2-2x+1}\)

\(=3x-\left|x-1\right|\)

\(=\left[{}\begin{matrix}3x-x+1\left(x\ge1\right)\\3x+x-1\left(x< 1\right)\end{matrix}\right.=\left[{}\begin{matrix}2x+1\\4x-1\end{matrix}\right.\)