Question

BT1: Tìm x, biết:

4) \(\text{|}0,4x-25\%\text{|}-4=3\)

Answer 1

\(\left|0,4x-25\%\right|-4=3\\ \left|\dfrac{2}{5}x-\dfrac{1}{4}\right|=3+4\\ \left|\dfrac{2}{5}x-\dfrac{1}{4}\right|=7\\ \Rightarrow\left\{{}\begin{matrix}\dfrac{2}{5}x-\dfrac{1}{4}=7\\\dfrac{2}{5}x-\dfrac{1}{4}=-7\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}\dfrac{2}{5}x=\dfrac{29}{4}\\\dfrac{2}{5}x=-\dfrac{27}{4}\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=\dfrac{145}{8}\\x=-\dfrac{135}{8}\end{matrix}\right.\)

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