Trả lời:
\(\left(\dfrac{2}{5}-3x\right)^2=\dfrac{9}{25}\)
\(\Leftrightarrow\left[{}\begin{matrix}\dfrac{2}{5}-3x=\dfrac{3}{5}\\\dfrac{2}{5}-3x=-\dfrac{3}{5}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}3x=-\dfrac{1}{5}\\3x=1\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-\dfrac{1}{15}\\x=\dfrac{1}{3}\end{matrix}\right.\)
Vậy x = -1/15; x = 1/3
Trả lời:
\(\left(\dfrac{2}{5}-3x\right)^2=\dfrac{9}{25}\)
\(\Leftrightarrow\left(\dfrac{2}{5}-3x\right)^2=\left(\dfrac{3}{5}\right)^2\) hoặc \(\left(\dfrac{2}{5}-3x\right)^2=\left(-\dfrac{3}{5}\right)^2\)
\(\Leftrightarrow\dfrac{2}{5}-3x=\dfrac{3}{5}\) hoặc \(\dfrac{2}{5}-3x=-\dfrac{3}{5}\)
\(\Leftrightarrow3x=\dfrac{2}{5}-\dfrac{3}{5}\) hoặc \(3x=\dfrac{2}{5}-\left(-\dfrac{3}{5}\right)\)
\(\Leftrightarrow3x=-\dfrac{1}{5}\) hoặc \(3x=1\)
\(\Leftrightarrow x=-\dfrac{1}{5}:3\) hoặc \(x=1:3\)
\(\Leftrightarrow x=-\dfrac{1}{15}\) hoặc \(x=\dfrac{1}{3}\)
Vậy ...