Câu hỏi của pham thi ngoc

Question

a) $\left|3\cdot x-1\right|=\left|5-2\cdot x\right|$

b) $\left|x+2\right|-\left|x+7\right|=0$

c) $\left|2\cdot x-1\right|+x=2$

d) $\left|x+1\right|+\left|2\cdot y-1\right|=0$

giúp mk nha 4...

Nguyễn Thanh Hằng · Accepted Answer

a/ $\left|3x-1\right|=\left|5-2x\right|$

$\Leftrightarrow\left[{}\begin{matrix}3x-1=5-2x\3x-1=-5+2x\end{matrix}\right.$

$\Leftrightarrow\left[{}\begin{matrix}3x+2x=5+1\3x-2x=-5+1\end{matrix}\right.$$\Leftrightarrow\left[{}\begin{matrix}5x=6\x=-4\end{matrix}\right.$ $\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{6}{5}\x=-4\end{matrix}\right.$

Vậy ......

b/ $\left|x+2\right|-\left|x+7\right|=0$

$\Leftrightarrow\left|x+2\right|=\left|x+7\right|$

$\Leftrightarrow\left[{}\begin{matrix}x+2=x+7\x+2=-x-7\end{matrix}\right.$

$\Leftrightarrow\left[{}\begin{matrix}x-x=7-2\x+x=-7-2\end{matrix}\right.$

$\Leftrightarrow\left[{}\begin{matrix}0x=5\left(loại\right)\2x=-9\end{matrix}\right.$

$\Leftrightarrow x=-\dfrac{9}{2}$

Vậy ...............

c/ $\left|2x-1\right|+x=2$

$\Leftrightarrow\left|2x-1\right|=2-x$

$\Leftrightarrow\left[{}\begin{matrix}2x-1=2-x\2x-1=-2+x\end{matrix}\right.$

$\Leftrightarrow\left[{}\begin{matrix}2x+x=2+1\2x-x=-2-1\end{matrix}\right.$

$\Leftrightarrow\left[{}\begin{matrix}3x=3\x=-3\end{matrix}\right.$

$\Leftrightarrow\left[{}\begin{matrix}x=1\x=-3\end{matrix}\right.$

Vậy ..Câu trả lời: a/ $\left|3x-1\right|=\left|5-2x\right|$