Giải bpt sau:
-1/(x-2)≥0
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\(a,\left(4x-1\right)\left(x^2+12\right)\left(-x+4\right)>0\)
\(\Leftrightarrow\left[{}\begin{matrix}4x-1>0\\x^2+12>0\left(LD\forall x\right)\\-x+4>0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}4x>1\\-x>-4\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x>\dfrac{1}{4}\\x< 4\end{matrix}\right.\)
Vậy \(S=\left\{x|\dfrac{1}{4}< x< 4\right\}\)
\(b,\left(2x-1\right)\left(5-2x\right)\left(1-x\right)< 0\)
\(\Leftrightarrow\left[{}\begin{matrix}2x-1< 0\\5-2x< 0\\1-x< 0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x< \dfrac{1}{2}\\x>\dfrac{5}{2}\\x< 1\end{matrix}\right.\)
Vậy \(S=\left\{x|1>x>\dfrac{5}{2}\right\}\)
\(x\left(x-1\right)>0\)
\(\Rightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x>0\\x-1>0\end{matrix}\right.\\\left\{{}\begin{matrix}x< 0\\x-1< 0\end{matrix}\right.\end{matrix}\right.\)\(\Rightarrow\left[{}\begin{matrix}x>1\\x< 0\end{matrix}\right.\)
\(bpt\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x-1\ge0\\4-x>0\end{matrix}\right.\\\left\{{}\begin{matrix}x-1\le0\\4-x< 0\end{matrix}\right.\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x\ge1\\x< 4\end{matrix}\right.\\\left\{{}\begin{matrix}x\le1\\x>4\end{matrix}\right.\end{matrix}\right.\Leftrightarrow1\le x< 4\)
Vậy .......
\(\left[{}\begin{matrix}\left\{{}\begin{matrix}x-1\ge0\\4-x>0\end{matrix}\right.\\\left\{{}\begin{matrix}x-1\le0\\4-x< 0\end{matrix}\right.\end{matrix}\right.\)⇔\(\left[{}\begin{matrix}\left\{{}\begin{matrix}x\ge1\\x< 4\end{matrix}\right.\\\left\{{}\begin{matrix}x\le1\\x>4\end{matrix}\right.\end{matrix}\right.\)
Vậy....
\(a,\frac{x+5}{x^2-2x+1}>0\)
\(\Leftrightarrow\frac{x+5}{\left(x-1\right)^2}>0\)
\(\Leftrightarrow x>-5\)
\(b,x^2+x+1>0\)
\(\Leftrightarrow\left(x^2+x+\frac{1}{4}\right)+\frac{3}{4}>0\)
\(\Leftrightarrow\left(x+\frac{1}{2}\right)^2+\frac{3}{4}>0\) ( luôn đúng)
Ta có: \(-\dfrac{1}{x-2}\ge0\)
nên x-2<0
hay x<2
\(-\dfrac{1}{x-2}\ge0\Leftrightarrow x-2\le0\Leftrightarrow x\le2\)
Mà : $x ≠ 2 $
Do đó, bất phương trình vô nghiệm