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\(\left|x-\dfrac{1}{3}\right|+\dfrac{4}{5}=\left|-3,2+\dfrac{2}{5}\right|\)
=>\(\left|x-\dfrac{1}{3}\right|+0,8=\left|-3,2+0,4\right|=2,8\)
=>\(\left|x-\dfrac{1}{3}\right|=2,8-0,8=2\)
=>\(\left[{}\begin{matrix}x-\dfrac{1}{3}=2\\x-\dfrac{1}{3}=-2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{7}{3}\\x=-\dfrac{5}{3}\end{matrix}\right.\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left|x-\dfrac{1}{3}\right|+\dfrac{4}{5}=\left|\left(-3,2\right)+\dfrac{2}{5}\right|\)
\(\Leftrightarrow\left|x-\dfrac{1}{3}\right|+\dfrac{4}{5}=\dfrac{14}{5}\)
\(\Rightarrow\left|x-\dfrac{1}{3}\right|=\dfrac{14}{5}-\dfrac{4}{5}\)
\(\Rightarrow\left|x-\dfrac{1}{3}\right|=2\)
\(\Rightarrow\left[{}\begin{matrix}x-\dfrac{1}{3}=2\\x-\dfrac{1}{3}=-2\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=\dfrac{7}{3}\\x=\dfrac{-5}{3}\end{matrix}\right.\)
Vậy..............
\(\left | x - \frac{1}{3} \right | + \frac{4}{5} = \left | \left ( - 3,2 \right ) + \frac{2}{5}\right |\)
\(\left | x - \frac{1}{3} \right | + \frac{4}{5} = \left | - \frac{14}{5} \right |\)
\(\left | x - \frac{1}{3} \right | + \frac{4}{5} = \frac{14}{5} \)
\(\left | x - \frac{1}{3} \right | = 2\)
* \(x - \frac{1}{3}= 2\)
x = 2 + \( \frac{1}{3}\)
\(x = \frac{7}{3}\)
* \(x - \frac{1}{3}= - 2\)
\(x = - 2 + \frac{1}{3}\)
\(x = - \frac{5}{3}\)
Vậy x = \(x = \frac{7}{3}; x = - \frac{5}{3}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\left|x-\frac{1}{3}\right|+\frac{4}{5}=\left|\left(-3,2\right)+\frac{2}{5}\right|\)
\(\left|x-\frac{1}{3}\right|+\frac{4}{5}=\left|\frac{-16}{5}+\frac{2}{5}\right|\)
\(\left|x-\frac{1}{3}\right|+\frac{4}{5}=\left|\frac{-14}{5}\right|\)
\(\left|x-\frac{1}{3}\right|+\frac{4}{5}=\frac{14}{5}\)
\(\left|x-\frac{1}{3}\right|=\frac{14}{5}-\frac{4}{5}\)
\(\left|x-\frac{1}{3}\right|=2\)
\(\Rightarrow\orbr{\begin{cases}x-\frac{1}{3}=2\\x-\frac{1}{3}=-2\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{7}{3}\\x=\frac{-5}{3}\end{cases}}\)
làm tiếp câu a) nhé
b) \(\left(x-7\right)^{x+1}-\left(x-7\right)^{x+11}=0\)
\(\left(x-7\right)^{x+1}.\left[1-\left(x-7\right)^{10}\right]=0\)
\(\Rightarrow\orbr{\begin{cases}\left(x-7\right)^{x+1}=0\\1-\left(x-7\right)^{10}=0\end{cases}}\Rightarrow\orbr{\begin{cases}x-7=0\\\left(x-7\right)^{10}=1\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=7\\x-7=1\end{cases}}\Rightarrow\orbr{\begin{cases}x=7\\x=8\end{cases}}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left\{\dfrac{-5< 0< -0,4}{x\in Z}\right\}\Rightarrow x\in\left\{-4;-3;-2;-1\right\}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\left|x-\dfrac{1}{3}\right|+\dfrac{4}{5}=\left|\left(-3,2\right)+\dfrac{2}{5}\right|\)
\(\Rightarrow\left|x-\dfrac{1}{3}\right|+0,8=\left|-3,2+0,4\right|\)
\(\Rightarrow\left|x-\dfrac{1}{3}\right|+0,8=2,8\)
\(\Rightarrow\left|x-\dfrac{1}{3}\right|=2\)
\(\Rightarrow\left[{}\begin{matrix}x-\dfrac{1}{3}=2\\x-\dfrac{1}{3}=-2\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{7}{3}\\x=\dfrac{-5}{3}\end{matrix}\right.\)
Bài này có 2 cách, cách 1 là xét 3 trường hợp, cách 2 là sử dụng phương pháp đánh giá. Trong bài này cách 2 ngắn hơn thì mình sẽ làm.
Điều kiện: x \(\ge\)0
Ta có: VT = |x - 3,2| + |2x - 0,2| = |3,2 - x| + |2x - 0,2| \(\ge\) |3,2 - x + 2x - 0,2| = |x + 3| = VP
Dấu "=" xảy ra <=> (3,2 - x)(2x - 0,2) \(\ge\) 0.
<=> \(\left[{}\begin{matrix}\left\{{}\begin{matrix}3,2-x\ge0\\2x-0,2\ge0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x\le3,2\\x\ge0,1\end{matrix}\right.\Leftrightarrow0,1\le x\le3,2}}\\\left\{{}\begin{matrix}3,2-x\le0\\2x-0,2\le0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x\ge3,2\\x\le0,1\end{matrix}\right.\Leftrightarrow x}\in\varphi}\end{matrix}\right.\)
Bài này you copy đúng k