Question

Tìm đk:

Answer 1

ĐKXĐ:

6.

\(\dfrac{3x+21}{-5}\ge0\Leftrightarrow3x+21\le0\)

\(\Leftrightarrow x\le-7\)

7.

\(\left(x^2+1\right)2x\ge0\Leftrightarrow2x\ge0\)

\(\Leftrightarrow x\ge0\)

8.

\(\left(-x^2-2\right)3x\ge0\Leftrightarrow3x\le0\)

\(\Leftrightarrow x\le0\)

9.

\(\left\{{}\begin{matrix}\dfrac{1}{\left(x-1\right)^2}\ge0\left(\text{luôn đúng}\right)\\x-1\ne0\end{matrix}\right.\) \(\Leftrightarrow x\ne1\) 

Answer 2

6) ĐKXĐ: \(x\le-7\)

7) ĐKXĐ: \(x\ge0\)

8) ĐKXĐ: \(x\in\varnothing\)

9) ĐKXĐ: \(x\ne1\)