Question

Tìm x, biết:

|3x−1|+|1−3x|=9

Answer 1

|3\(x\) - 1| +|1 - 3\(x\)| = 9

vì |3\(x\) - 1| = |1 - 3\(x\)| nên:

|3\(x\) - 1| + |1 - 3\(x\)| = |3\(x\) - 1| + |3\(x\) - 1| = 2|3\(\)\(x\) - 1|

⇒2.|3\(x\) - 1| = 9

      |3\(x\) - 1| = \(\dfrac{9}{2}\)

      \(\left[{}\begin{matrix}3x-1=\dfrac{-9}{2}\\3x-1=\dfrac{9}{2}\end{matrix}\right.\)

       \(\left[{}\begin{matrix}3x=-\dfrac{9}{2}+1\\3x=\dfrac{9}{2}+1\end{matrix}\right.\)

        \(\left[{}\begin{matrix}3x=-\dfrac{7}{2}\\3x=\dfrac{11}{2}\end{matrix}\right.\)

         \(\left[{}\begin{matrix}x=-\dfrac{7}{6}\\x=\dfrac{11}{6}\end{matrix}\right.\)

       Vậy \(x\) \(\in\) {- \(\dfrac{7}{6}\); \(\dfrac{11}{6}\)}