Câu 4. (1 điểm) Tìm số thực x. a) 1$\frac{1}{2}$ + $\frac{4}{5}$x = $\frac{5}{6}$ b) $\frac{5}{2}$ - |x + $\frac{1}{2}$| = $\frac{3}{4}$

`a)1\1/2+4/5x=5/6`

`=>3/2+4/5x=5/6`

`=>4/5x=5/6-3/2`

`=>4/5x=(-2)/3`

`=>x=(-2)/3:4/5`

`=>x=(-5)/6`

`Vậy` `x=(-5)/6`

`b)5/2-|x+1/2|=3/4`

`=>|x+1/2|=5/2-3/4`

`=>|x+1/2|=7/4`

`=>`\(\left[ \begin{array}{l}x+\dfrac12=\dfrac74\\x+\dfrac12=\dfrac{-7}4\end{array} \right.\) 

`=>`\(\left[ \begin{array}{l}x=\dfrac74-\dfrac12\\x=\dfrac{-7}4-\dfrac12\end{array} \right.\) 

`=>`\(\left[ \begin{array}{l}x=\dfrac74-\dfrac24\\x=\dfrac{-7}4-\dfrac24\end{array} \right.\) 

`=>`\(\left[ \begin{array}{l}x=\dfrac54\\x=\dfrac{-9}4\end{array} \right.\) 

`Vậy` `x\in{5/4;(-9)/4}`