Question

BT1: Tìm x, biết:

5) \(\text{|}x+\dfrac{1}{2}\text{|}+\text{|}x+\dfrac{1}{3}\text{|}+\text{|}x+\dfrac{1}{4}\text{|}=4x\)

Answer 1

\(\left|x+\dfrac{1}{2}\right|+\left|x+\dfrac{1}{3}\right|+\left|x+\dfrac{1}{4}\right|=4x\)

Mà \(\left\{{}\begin{matrix}\left|x+\dfrac{1}{2}\right|\ge0\\\left|x+\dfrac{1}{3}\right|\ge0\\\left|x+\dfrac{1}{4}\right|\ge0\end{matrix}\right.\)

\(\Leftrightarrow\left|x+\dfrac{1}{2}\right|+\left|x+\dfrac{1}{3}\right|+\left|x+\dfrac{1}{4}\right|\ge0\)

\(\Leftrightarrow4x\ge0\)

\(\Leftrightarrow x+\dfrac{1}{2}+x+\dfrac{1}{3}+x+\dfrac{1}{4}=4x\)

\(\Leftrightarrow3x+1=4x\)

\(\Leftrightarrow x=1\left(tm\right)\)

Vậy ..