Question

Tìm x

25. ( 3x - \(\dfrac{1}{2}\))\(^2\) = 16

Answer 1

\(25\cdot\left(3x-\dfrac{1}{2}\right)^2=16\)

\(\Rightarrow\left(3x-\dfrac{1}{2}\right)^2=\dfrac{16}{25}\)

\(\Rightarrow\left(3x-\dfrac{1}{2}\right)^2=\left(\pm\dfrac{4}{5}\right)^2\)

\(\Rightarrow\left[{}\begin{matrix}3x-\dfrac{1}{2}=\dfrac{4}{5}\\3x-\dfrac{1}{2}=-\dfrac{4}{5}\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}3x=\dfrac{13}{10}\\3x=-\dfrac{3}{10}\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{13}{30}\\x=-\dfrac{1}{10}\end{matrix}\right.\)

Vậy \(x\in\left\{\dfrac{13}{30};-\dfrac{1}{10}\right\}\).

P/s: Mình ko nghĩ đây là bài toán của lớp 5.