a) Để \(\sqrt{\dfrac{x}{3}}\) có nghĩa thì \(\dfrac{x}{3}\ge0\Leftrightarrow x\ge0\)

b) Để \(\sqrt{-5x}\) có nghĩa thì \(-5x\ge0\Leftrightarrow x\le0\)

c) Để \(\sqrt{4-x}\) có nghĩa thì \(4-x\ge0\Leftrightarrow x\le4\)

d) Để \(\sqrt{3x+7}\) có nghĩa thì \(3x+7\ge0\Leftrightarrow x\ge-\dfrac{7}{3}\)

e) Để \(\sqrt{-3x+4}\) có nghĩa thì \(-3x+4\ge0\Leftrightarrow x\le\dfrac{4}{3}\)

f) Để \(\sqrt{\dfrac{1}{-1+x}}\) có nghĩa thì \(\left\{{}\begin{matrix}\dfrac{1}{-1+x}\ge0\\-1+x\ne0\end{matrix}\right.\)

\(\Leftrightarrow-1+x>0\Leftrightarrow x>1\)

g) Để \(\sqrt{1+x^2}\) có nghĩa thì \(1+x^2\ge0\left(đúng\forall x\right)\)

h) \(\sqrt{\dfrac{5}{x-2}}\) có nghĩ thì \(\left\{{}\begin{matrix}\dfrac{5}{x-2}\ge0\\x-2\ne0\end{matrix}\right.\)

\(\Leftrightarrow x-2>0\Leftrightarrow x>2\)

a. \(x\ge0\)

b. \(x< 0\)

c. \(x\le4\)

d. \(x\ge\dfrac{-7}{3}\)

e. \(x\le\dfrac{4}{3}\)

f. \(x>1\)

g. Mọi x

h. \(x>2\)

a) ĐKXĐ: \(x\ge2\)

b) ĐKXĐ: \(\left[{}\begin{matrix}x\le1\\x\ge2\end{matrix}\right.\)

c) ĐKXĐ: \(\dfrac{x+3}{5-x}\ge0\)

\(\Leftrightarrow\dfrac{x+3}{x-5}\le0\)

\(\Leftrightarrow\left\{{}\begin{matrix}x+3\ge0\\x-5< 0\end{matrix}\right.\Leftrightarrow-3\le x< 5\)

giúp mình với ạ :(((

a) \(\sqrt{\dfrac{a}{3}}\) có nghĩa khi: \(\dfrac{a}{3}\ge0\Leftrightarrow a\ge0\)

Vậy \(a\ge0\) thì \(\sqrt{\dfrac{a}{3}}\) xác định

b) \(\sqrt{-5a}\) có nghĩa khi \(-5a\ge0\Leftrightarrow a\le0\)

Vậy \(a\le0\) thì \(\sqrt{-5a}\) xác định

c) \(\sqrt{4-a}\) có nghĩa khi \(4-a\ge0\Leftrightarrow-a\ge-4\Leftrightarrow a\le4\)

Vậy \(a\le4\) thì \(\sqrt{4-a}\) xác định

a: ĐKXĐ: \(a\ge0\)

b: ĐKXĐ: \(a\le0\)

c: ĐKXĐ: \(a\le4\)

$a)ĐK:8x+2\ge 0$

$\to 8x \ge -2$

$\to x \ge -\dfrac14$

$b)ĐK:\dfrac{-5}{6-3x} \ge 0(x \ne 2)$

Mà $-5<0$

$\to 6-3x<0$

$\to 6<3x$

$\to x>2$

$*A=x-2\sqrt{x-2}+3(x \ge 2)$

$=x-2-2\sqrt{x-2}+1+4$

$=(\sqrt{x-2}-1)^2+4 \ge 4$

Dấu "=" xảy ra khi $\sqrt{x-2}-1=0 \Leftrightarrow \sqrt{x-2}=1\Leftrightarrow x=3$

a) \(x\ge-\dfrac{1}{4}\)

b) x<2

a) ĐKXĐ: \(x\in R\)

b) ĐKXĐ: \(-2\sqrt{2}+2\le x\le2\sqrt{2}+2\)

Để \(\sqrt{\dfrac{1}{3-2x}}\) có nghĩa

Khi\(\dfrac{1}{3-2x}\ge0\)

\(\Leftrightarrow3-2x>0\)

\(\Leftrightarrow-2x< -3\)

\(\Leftrightarrow x>\dfrac{3}{2}\)

ĐKXĐ: \(x< \dfrac{3}{2}\)

a) \(\sqrt{x^2-x+1}\)

\(=\sqrt{x^2-2\cdot\dfrac{1}{2}\cdot x+\dfrac{1}{4}+\dfrac{3}{4}}\)

\(=\sqrt{\left(x-\dfrac{1}{2}\right)^2+\dfrac{3}{4}}\)

Mà: \(\left(x-\dfrac{1}{2}\right)^2+\dfrac{3}{4}\ge\dfrac{3}{4}>0\forall x\)

Nên bt luôn có nghĩa

b) \(\dfrac{5}{\sqrt{1-\sqrt{x-1}}}\) có nghĩa khi:

\(\left\{{}\begin{matrix}x-1\ge0\\1-\sqrt{x-1}>0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x\ge1\\x-1< 1\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}1\le x\\x< 2\end{matrix}\right.\Leftrightarrow1\le x< 2\)

c) \(\dfrac{\sqrt{x}-1}{\sqrt{x}+1}\) có nghĩa khi:

\(x\ge0\)

d) \(\dfrac{\sqrt{-3x}}{x^2-1}\) có nghĩa khi:

\(\Leftrightarrow\left\{{}\begin{matrix}-3x\ge0\\x^2-1\ne0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x\le0\\x\ne\pm1\end{matrix}\right.\)

e) \(\dfrac{2}{\sqrt{x}-2}\) có nghĩa khi:

\(\left\{{}\begin{matrix}x\ge0\\\sqrt{x}-2\ne0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x\ge0\\x\ne4\end{matrix}\right.\)

\(\sqrt{\dfrac{1}{-1+x}}=\sqrt{\dfrac{1}{x-1}}\) có nghĩa khi:

\(\left\{{}\begin{matrix}\dfrac{1}{x-1}\ge0\\x-1\ne0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x-1\ge0\\x\ne1\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x\ge1\\x\ne1\end{matrix}\right.\)

\(\Leftrightarrow x>1\)

\(ĐKXĐ:\dfrac{1}{-1+1x}>0\Leftrightarrow-1+1x< 0\\ \Leftrightarrow x< -1\)