Câu 3: (1,5 điểm) Tìm x biết: a) 2x - $\frac{1}{3}$ = $\sqrt{\frac{25}{9}}$ b) |x + 1,5| = $\frac{5}{2}$

`a . ` `2x-1/3=\sqrt{25/9}`

`=>` `2x-1/3=\sqrt{(5/3)^2}`

`=>` `2x-1/3=5/3`

`=>` `2x=5/3+1/3`

`=>` `2x=2`

`=>` `x=1`

Vậy `x=1`

$\\$

`b . ` `|x+1,5|=5/2`

`=>` $\left[\begin{matrix} x+1,5=\dfrac{5}{2}\\ x+1,5=-\dfrac{5}{2}\end{matrix}\right.$

`=>` $\left[\begin{matrix} x=\dfrac{5}{2}-1,5\\ x=-\dfrac{5}{2}-1,5\end{matrix}\right.$

`=>` $\left[\begin{matrix} x=1\\ x=-4\end{matrix}\right.$

Vậy `x \in {1 ; -4 }`

`#me`