Giải bpt
(m2+1)x+1<m
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\(x\left(x-1\right)>0\)
\(\Rightarrow\left[{}\begin{matrix}\left\{{}\begin{matrix}x>0\\x-1>0\end{matrix}\right.\\\left\{{}\begin{matrix}x< 0\\x-1< 0\end{matrix}\right.\end{matrix}\right.\)\(\Rightarrow\left[{}\begin{matrix}x>1\\x< 0\end{matrix}\right.\)
\(\Leftrightarrow\dfrac{x^2+x+2-2x^2-2x-2}{\left(x^2+x+1\right)\left(x^2+x+2\right)}>0\)
=>-x^2-x>0
=>x(x-1)<0
=>0<x<1
\(x^2-1>0\Rightarrow x^2>1\Rightarrow\left|x\right|>1\Rightarrow\left[{}\begin{matrix}x>1\\x< -1\end{matrix}\right.\)
ĐKXĐ: \(x^2+x-1\ge0\)
\(\Rightarrow3x^2-x+1>3\sqrt{\left(x^2-x+1\right)\left(x^2+x-1\right)}\)
Đặt \(\left\{{}\begin{matrix}\sqrt{x^2-x+1}=a>0\\\sqrt{x^2+x-1}=b\ge0\end{matrix}\right.\)
\(\Rightarrow2a^2+b^2>3ab\)
\(\Leftrightarrow\left(2a-b\right)\left(a-b\right)>0\)
\(\Rightarrow\left[{}\begin{matrix}2a< b\\a>b\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}2\sqrt{x^2-x+1}< \sqrt{x^2+x-1}\\\sqrt{x^2-x+1}>\sqrt{x^2+x-1}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}4\left(x^2-x+1\right)< x^2+x-1\\x^2-x+1>x^2+x-1\end{matrix}\right.\)
\(\Leftrightarrow...\) (nhớ kết hợp ĐKXĐ ban đầu)
\(\left(x-3\right)\left(x+1\right)\left(2-3x\right)>0.\)
\(x\) | \(-\infty\) \(-1\) \(\dfrac{2}{3}\) \(3\) \(+\infty\) |
\(x-3\) | - | - | - 0 - |
\(x+1\) | - 0 + | + | + |
\(2-3x\) | + | + 0 - | - |
\(\left(x-3\right)\left(x+1\right)\left(2-3x\right).\) | + 0 - 0 + 0 + |
Vậy \(\left(x-3\right)\left(x+1\right)\left(2-3x\right)>0\) khi \(x\in\left(-\infty;-1\right)\cup\left(\dfrac{2}{3};3\right)\cup\left(3;+\infty\right).\)
\(\frac{x-3}{x-1}>1\)
\(\Leftrightarrow\frac{x-3}{x-1}-\frac{x-1}{x-1}>0\)
\(\Leftrightarrow\frac{x-3-x+1}{x-1}>0\)
\(\Leftrightarrow\frac{-2}{x-1}>0\)
\(\Leftrightarrow x-1< 0\)
\(\Leftrightarrow x< 1\)
ĐK: \(x\ne\dfrac{1}{2};x\ne-\dfrac{1}{3}\)
\(\dfrac{x+2}{3x+1}\ge\dfrac{x-2}{2x-1}\)
\(\Leftrightarrow\dfrac{\left(x+2\right)\left(2x-1\right)-\left(x-2\right)\left(3x+1\right)}{\left(3x+1\right)\left(2x-1\right)}\ge0\)
\(\Leftrightarrow\dfrac{2x^2+3x-2-3x^2+5x+2}{6x^2-x-1}\ge0\)
\(\Leftrightarrow\dfrac{-x^2+8x}{6x^2-x-1}\ge0\)
\(\Leftrightarrow\left\{{}\begin{matrix}-x^2+8x\ge0\\6x^2-x-1>0\end{matrix}\right.\left(1\right)\) hoặc \(\left\{{}\begin{matrix}-x^2+8x\le0\\6x^2-x-1< 0\end{matrix}\right.\left(2\right)\)
\(\left(1\right)\Leftrightarrow\left\{{}\begin{matrix}0\le x\le8\\\left[{}\begin{matrix}x>\dfrac{1}{2}\\x< -\dfrac{1}{3}\end{matrix}\right.\end{matrix}\right.\Leftrightarrow\dfrac{1}{2}< x\le8\)
\(\left(2\right)\Leftrightarrow\left\{{}\begin{matrix}\left[{}\begin{matrix}x\le0\\x\ge8\end{matrix}\right.\\-\dfrac{1}{3}< x< \dfrac{1}{2}\end{matrix}\right.\Leftrightarrow-\dfrac{1}{3}< x\le0\)
Vậy ...
\(\left(m^2+1\right)x+1< m\\ \Leftrightarrow\left(m^2+1\right)x< m-1\\ \Leftrightarrow x< \dfrac{m-1}{m^2+1}\left(\text{Vì }m^2+1\ne0\right)\)