Question

[Giang シ)]

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Answer 1

[Nguyễn Lê Phước Thịnh]

\(\Leftrightarrow\left[{}\begin{matrix}3x-\dfrac{2}{5}=\dfrac{4}{5}\\3x-\dfrac{2}{5}=-\dfrac{4}{5}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}3x=\dfrac{6}{5}\\3x=-\dfrac{2}{5}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{5}\\x=-\dfrac{2}{15}\end{matrix}\right.\)

Answer 2

[Nguyễn Tân Vương]

\(\left(\dfrac{2}{5}-3x\right)^2=\left(\dfrac{-4}{5}\right)^2\)

\(\text{Vậy}\dfrac{2}{5}-3x=\left(\dfrac{-4}{5}\right)\)

               \(3x=\dfrac{2}{5}+\dfrac{4}{5}=\dfrac{6}{5}\) 

                \(x=\dfrac{6}{5}:3=\dfrac{2}{5}\)

\(\text{hoặc}\dfrac{2}{5}-3x=\dfrac{4}{5}\)

               \(3x=\dfrac{2}{5}+\left(\dfrac{-4}{5}\right)=\left(\dfrac{-2}{5}\right)\)

                 \(x=\dfrac{-2}{5}:3=\dfrac{-2}{15}\)

\(\Rightarrow x\in\left\{\dfrac{2}{5};\dfrac{-2}{15}\right\}\)

\(\text{Hok tốt!}\)