Question

20. Tìm x biết : a)| 5/3 x|=|- 1/6 |; b)| 3/4 x- 3/4 |- 3/4 =|- 3/4 |; c)|x+ 3/5 |-|x- 7/3 |=0

Answer 1

a: \(\Leftrightarrow\left|\dfrac{5}{3}x\right|=\dfrac{1}{6}\)

\(\Leftrightarrow\left[{}\begin{matrix}x\cdot\dfrac{5}{3}=\dfrac{1}{6}\\x\cdot\dfrac{5}{3}=-\dfrac{1}{6}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{6}:\dfrac{5}{3}=\dfrac{3}{30}=\dfrac{1}{10}\\x=-\dfrac{1}{10}\end{matrix}\right.\)

b: \(\Leftrightarrow\left|\dfrac{3}{4}x-\dfrac{3}{4}\right|=\dfrac{3}{4}+\dfrac{3}{4}=\dfrac{3}{2}\)

\(\Leftrightarrow\left|x-1\right|=\dfrac{3}{2}:\dfrac{3}{4}=2\)

=>x-1=2 hoặc x-1=-2

=>x=3 hoặc x=-1

c: \(\Leftrightarrow\left|x+\dfrac{3}{5}\right|=\left|x-\dfrac{7}{3}\right|\)

\(\Leftrightarrow x+\dfrac{3}{5}=\dfrac{7}{3}-x\)

=>2x=44/15

hay x=22/15